Scheerer-The Blowpipe Manual

7/31/2019 Scheerer-The Blowpipe Manual

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S. F. PECKHAM.


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THE

Blowpipe ManualBY

DR. THEODORE SCHEERER,raORaSOR or CHEHISTBT in the royal SAXOX UIHING schoolat rSKIBXBO.

TRJlHSLATZD bt

WILLIAM S. CLARK.

FOlt COPIKS OF THLS BOOK, APPLY TOW. S. CLARK, AMHERST, MASS.

Price 75 Cents.


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Translator's Preface.

This little manual has been prepared for the use of thestudents of the Massachusetts Agricultural College.

Those who desire further information upon this mostimportant subject are referred to Plattner's " Art ofAssaying with the Blowpipe."


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Contents.USE OF THE BLOWPIPE IN QUALITATIVE ANALYSIS.

Page.Introduction, ...... 9

I. The Blowpipe Flame and Articles necessary in assayingqualitatively with the Blowpipe, . . .13

Oxidizing and Reducing Flames, . . .13A. The Blowpipe, ...... 15B. The Blowpipe Flame, ..... 16C. Supports and Holders for the substances to be heated, 16(1) Charcoal, p 16. (2) Platinum Wire, p 17. (3)

Platinum Foil, p 18. (4) Platinum Spoon, p 18. (6)Platinum Forceps, p 18. (6) Glass Tubes, p 18. (7)Glass Matrasses, p 19.

D. Blowpipe Reagents, ..... 19(1) Soda, p 19. (2) Borax, p 19. (3) Salt of Phos-phorus, p 20. (4) Other Reagents, p 20.E. Other Articles for use with the Blowpipe, . . 21II. Qualitative Examination with the Blowpipe, . 22

Order of the Tests, . . . .221. Test in Glass Matrass, . . .22

Substances which, under certain circumstances, may' be detected in this way : Water, Sulphur, Selenium,Tellurium, Arsenic, Quicksilver, Oxygen, Ammonia,Fluorine, Chlorine, Bromine, Iodine, Nitric Acid.

2. Test in open Glass Tube, . . . .25Substances which, under certain circumstances, maybQ detected in this way : Sulphur, Selenium, Telluri-um, Arsenic, Antimony.


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CONTENTS. VI3. Test on Charcoal, ..... J6

Substances which may be determined by the Incrus-tation which they give to the coal : Selenium, Telluri-um, Arsenic, Antimony, Bismuth, Lead, Cadmium,Zinc, Tin, Molybdenum, Silver, Metallic Sulphides,Chlorides, Bromides and Iodides.

4. Test in the Platinum Forceps, (as well as, in somecases, on the platinum wire or coal,) . . 34Substances which may be detected by the Color whichthey communicate to the blowpipe flame : Soda, Po-tassa, Caesia, Rubidia, Lithia, Strontia, Lime, Baryta,Molybdic Acid, Oxide of Copper, Tellurous Acid,Phosphoric Acid, Boracic Acid, Thallium, Arsenic,Antimony, Lead, Indium, Selenium, Chloride andBromide of Copper.

5. Test in the Borax Bead, .. . . .426. Test in the Phosphorus Bead, . . .43Substances which may be determined especially by

the Colors which they impart to the Beads of Boraxand Salt of Phosphorus : Oxides of Cerium, Lantha-num, Didymium. Manganese, Iron, Cobalt, 'Nickel,Zinc, Cadmium, Indium, Lead, Thallium, Tin, Bis-muth, Uranium, Copper, Silver, Platinum, Palladium,Rhodium, Iridium, Ruthenium and Gold, Titanic, Co-lumbic, Niobic, Antimonious, Tungstic, Molybdic,Vanadic, Chromic and Tellurous Acids.

Table I, in which the above substances are arranged accord-ing to the Colors which they give the beads of Boraxand Salt of Phosphorus, . . . .44

Table II. On the Behavior of Metallic Oxides when heatedalone upon Charcoal ; with Carbonate of Soda on Char-coal ; and in the Beads of Borax and Salt of Phospho-rus on the Platinum Wire, . . . .52

Table III. On the Behavior of the Alkaline Earths andEarths Proper before the Blowpipe, . . . ^''^^e7. Test with Soda, . . . . . 70Substances which, under certain circumstances, may


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Vn CONTENTS.be detected in this way : Silicic, Titanic, Tungstic andMolybdic Acids, Gold, Silver, Platinum, Tungsten, .Molybdenum, Antimony, Arsenic, Tellurium, Copper,Bismufli, Tin, Lead, Thallium, Zinc, Cadmium, Indi-um, Nickel, Cobalt, Iron.

8. Special Tests for the determination of certain sub-stances, ...... 71These substances are : Potassa, Lithia, Boracic Acid,Sulphuric Acid and Sulphur, Nitric Acid, Fluorine,Chlorine, (Chlorides and Chlorates), Bromine, (Bro-mides and Bromates,) Iodine, (Iodides and lodates).Magnesia, Columbic Acid, Alumina, Oxides of Zinc,Tin and Antimony, Titanic and Niobic Acids, Zirco-nia, Oxide of Magnesia, Tellurium, Arsenic, Phos-phorus.

ABBREVIATIONS EMPLOYED IN TABLES II. AND III.

Bx.Borax or Biborate of Soda.Ch.Charcoal.Ct.Coating or Incrustation. OFl.Oxidizing Flame.RFl.Reducing Flame.Sd.Carbonate of Soda.SPh.Salt of Phosphorus or microcosmic salt, a phos-

phate of soda, ammonia and water, which when heatedloses its water and ammonia and becomes a monobasicphosphate of soda.


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CONTENTS. VIII

Alphabetical List of Certain Substances which, may beDetected with the Aid of the Blowpipe.

Alumina, p 44, 66, 80.Antimony, p 26, 27, 41, 44, 52,

71, 80.Arsenic, p 25, 27, 41, 52, 71, 81.Baryta, p 37, 44, 66.Bismuth, p 28, 44, 52, 71.Boracic Acid, p 40, 73.Bromine, p 33, 78.Cadmium, p 29, 44, 52.Cassium, p 35.Cerium, p 45, 54.Clilorine, p 33, 78.Fluorine, p. 76.Glucina, p. 44, 68.Chromium, p 45, 64.Cobalt, p 45, 64, 71.Columbic Acid, p 44, 80.Copper, p 38, 42, ^5, 54.Didymium, p 45.Fluorine, p 75.Glucina, p 44, 68.Gold, p 56, 70.Indium, p 29, 42, 44, 86.Iodine, p 33, 79.Iron, p 46, 66, 71.Lanthanum, p 44.Lead, p 28, 42, 44, 66.Lithia, p 32, 35, 72.

Magnesia, p 44, 66, 80.Manganese, p 45, 66, 81.Mercury, p 23, 58.Molybdic Acid, p 30, 38, 44, 68.Nickel, p 45, 66, 71Niobic Acid, p 44, 81.Nitric Acid, p 75.Pho.sphoric Acid, p 39, 83.Platinum, p 70.Potassa, p 36, 72.Eubidium, p 36.Selenium, p 23, 26, 26, 42.Silica, p 44, 71, 74.Silver, p 31, 44, 60.Soda, p 34.Strontia, p 36, 44, 66.Sulphur, p 25, 31, 74.Tellurium, p 23, 27, 39, 44, 60,

81.Thallium, p 29, 44, 44, 60.Tin, p 30, 44, 60, 80.Titonic Acid, p 44, 62, 80.Vanadic Acid, p 45, 62.Uranium, p 45, 62.Yttria, p 44,^I9-Zinc, p 29, 44, 46, 80.Ziiconia, p 44, 68, 80.


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Introduction.

' The blowpipe is a simple instrument which has forseveral centuries been used by workers of metals invarious countries to produce suddenly an intense heat.Its use having been chiefly to melt the solder employedin fastening together pieces of more infusible metals, itis called by the Germans soldering pipe. The simplestand most ancient form of the blowpipe is a hollow, coni-cal, metallic tube, which at the small end is bentwithout a sharp turn to a right angle. In using, thelarger end of this is taken into the mouth and a streamof air blown into it, which is applied as it issues fromthe point exactly like the blast from a bellows. Theblowpipe may, therefore, be regarded as a small bellowsfed by the mouth, and its lieatinof effect depends uponthe same principles. In this rude application and formthe blowpipe was of no importance to science. This itcame first to possess when the careful study of severalscientific men had converted it into one of themost valuable instruments for the chemist and mineralo-gist, as well as for miners and metallurgists. The fol-


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10 INTRODUCTION.lowing historical sketch shows how this was graduallyaccomplished.

Anthony Swab, a Swedish counselor of mines, wholived in the first half of the eighteenth centurj, was, sofar as is known, the first who undertook to apply theblowpipe to the chemical examination of ores andminerals. Next to him, the Swedish mineralogist Cron-stedt, used the blowpipe for determining and distinguish-ing minerals, with special reference to the chemical sys-tem of mineralogy published by him in 1758. Enges-troem, who in the year 1765 translated this system intoEnglish, added a description of Cronstedt's method ofusing {he blowpipe. In the year 1773 this descriptionas translated into Swedish, and soon after, into severalother European languages. Imperfect as the applicationof the blowpipe then was, it attracted immediately greatattention from the rapidity and certainty of its results.Nevertheless, the new art, which easy as it appearedrequired long continued practice, made at first but littleprogress. It received important assistance from theeflforts of Bergraann, who employed the blowpipe forqualitative examinations in the whole province of inor-ganic chemistry, and showed how by its aid very mi-nute quantities of mineral substances could be detected,the discovery of which in any other way would be muchmore difficult. Bergmann published the results of hisexperiments in a work, which was printed in Latin atVienna in 1779, and was translated into Swedish byHjelm in 1781. Upon the death of Bergmann, whichhappened soon after, (in 1784), Gahn pursued still


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INTRODUCTION. 11further the path struck out by the latter. He attainedby persevering zeal to great skill in the use of theblowpipe, -without, however, recording anything of hisrich experience, which would have been for the mostpart lost except for his obliging readiness to com-municate the art to any one desirous of acquiringit. The young Berzelius, whom Gahn regardedwith peculiar interest as a student of science, was thusenabled to possess himself of his knowledge, and uponthis foundation to build greater. Gahn had made agood selection ; a person better adapted for this furtherdevelopment of the art could scarcely have been found.By him the application of the blowpipe was not only ina high degree perfected and extended, but at the sametime by his personal instructions and writings so widelydiffused that it has now become an essential partof the knowledge of every chemist and mineralogist.In the year 1821 Berzelius published his excellent''Use of the Blowpipe in Chemistry and Mineralogy,'*of which since that time several editions have appearedand which has been translated for the use of Americanstudents by Professor J. D. "Whitney.

All the efforts of those who thus far had used theblowpipe in chemical experimentation had been directedto qualitative analysis. Harkort, however, seizing uponthe fruitful idea of employing the blowpipe also inquantitative analysis became the founder of a new branchof the blowpipe art. In 1827 appeared as the resultof his experiments made in Freiberg the first numberof his "Art of Assaying with the Blowpipe" containing


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12 INTRODUCTION.the article on silver. He was prevented from issuingthe second number, which was to contain the methodsof determining lead, copper and tin, by a call to Mexico,where he died a few years after. Plattner, his succes-sor, perceiving the importance of developing the subject,employed himself for many years in applying to prac-tice the idea of Harkort. His perseverance and in-genuity enabled him to bring the art of assaying quanti-tatively with the blowpipe to a degree of perfectionwhich had been previously thought impossible. Plattnerhas given the results of his experiments both in qualita-tive and quantitative assaying in his work, "Art ofAssaying with the Blowpipe," of which the first editionappeared in 1835 and the second in 1847, and whichhas been translated and published in London.The methods of assaying qualitatively and quantita-

tively with the blowpipe, in the state of perfection towhich they have been brought by Berzelius and Platt-ner, are sciences so extensive that a considerable amountof time and practice are required to become familiar withthem. Especially is this true of quantitative assaying,which indeed is seldom acquired by chemists, but isalmost exclusively employed by practical metallurgists.

The following description of the apparatus, reagentsand methods to be employed in qualitative analysis withthe blowpipe, is believed to be sufficient for the use ofbeginners, and even for most of the students in thescientific schools and colleges of the country.


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I.THE BLOWPIPE FLAME AND ARTICLES NECESSARY FOR

ASSAYING QUALITATIVELY WITH THE BLOWPIPE.

The blowpipe flame is produced when with the aidof a blowpipe a current of air is driven in accordancewith certain rules through the flame of a candle orlamp. The best flame for this purpose is that of anoil lamp with a wide and rather thick wick. The prin-cipal requisites to the production of a good flame arefirst, the steadiness and sufficient durability of the blastand secondly, the proper application and management ofthe same. The first will be treated of along with thedescription of the blowpipe. In regard to the secondpoint, the flame may be made to produce upon theheated substance either an oxidizing or a reducingeffect.The oxidizing and reducing flames are the principal

agents in the whole art of assaying with the blowpipe.He who understands how to produce these flames ofthe right kind and of sufficient permanence has over-come one of its most difficult points.

To form a reducing flame, the point or jet ofthe blowpipe is held parallel with the somewhat


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14 BLOWPIPE FLAMES.obliquely cut vrick and in such a way that it justtouches the side of the flame. The result will bea yellow, luminous flame.An oxidizing flame is produced when the blowpipe

jet is introduced into the flame about one-third thewidth of the wick. At the same time it is well to blowa little harder than in the production of the reducingflame. The oxidizing flame is of a blue color andpossesses but little illuminating power.

The yellow color and luminous character of the re-ducing flame result from the solid particles of carbon,which unconsumed, but white-hot, float in the burninggases till they are burnt upon the outside of the conicalflame. In the oxidizing flame, which exhibits the bluecolor of burning carbonic oxide gas, these particles ofcarbon are wanting.

It is not difficult to give the reason for the productionof these unlike flames. In the reducing flame the lesspowerful blast from the blowpipe drives the whole flamebefore it without causing a complete mixture of the com-bustible gases with the air ; while in the oxidizing flamea more powerful stream of air is thrown directly intothe flame, and is thus more thoroughly mixed with theburning gases. In the latter case, therefore, a muchmore complete combustion must take place than in theformer.

If a piece of a substance capable of oxidation be helddirectly before the point of the oxidizing flame, it willbe heated by it, and will be oxidized by the surroundingatmospheric air. If a powerful blast be used in this


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THE BLOWPIPE. 15operation, a portion of tho air will pass unconsumcdthrough the point of the flame and increase its oxidiz-ing effect. Not only is the oxidizing flame employedfor oxidation, but also, on account of the greater inten-sity of its heat, for determining the fusibility of sub-stances. It should here be observed that the point isthe hottest part of the flame.The reducing flame has the greatest reducing eiSTect

when the substance operated on is introduced so far intothe flame as to be completely surrounded by it and thusprotected from the oxidizing influences of the atmos-pheric air. It must not, however, be introduced so farinto it as to allow it to become covered with carbon,which would diminish the heat, and sometimes produceother injurious efiects.

A. The Blowpipe.The most convenient form of the blowpipe is that in-

vented by Berzelius. It consists of five parts, whichare so fitted together that they can be readily takenapart for cleansing or transportation. These parts are amouthpiece, a narrow tube seven to nine inches long, anair-chamber to collect the condensed vapor of the breath,a small tube inserted into the air-chamber at right-anglesto the larger one, and a jet with a minute orifice for theescape of the blast.

The mouthpiece may be either funnel-shaped to pressagainst the lips, in which case it is made of horn, or amere extension of the larger tube, formed of bone, ivoryor silver, the tube itself being usually of brass.


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16 SUPPORTS FOR ASSAY.The jet should be a conical piece of platinum pro-

perly bored and drilled to fit the tip of the shorter tubeand to allow the escape of a very small stream of air.Care must be taken that the orifice be not too much en-larged in removing the carbon which may collect uponand obstruct it. This is best done by heating the jet toredness.With sufficient practice it is possible by using the

wide mouthpiece to blow uninterruptedly from five toten minutes. During this continuous blowing the ex-perimenter must breathe through the nose, using thepalate as a valve, and force the air out by means of themuscles of the cheeks.

B. The Blowpipe Flame.The flame for use with the blowpipe may be that of

coal gas, a candle, or a lamp filled with oil, burningfluid or alcohol. Where gas cannot be had, it will befound convenient to have both an alcohol and an oillamp. These may be either of glass or metal.C. Supports and Holders for the Substances

TO BE Heated.For holding the substances which are to be exposed

to the flame of the blowpipe must be employed, ofcourse, materials which are not easily injured by heat.The following articles are most commonly used :

1. Charcoal.The best for this purpose is a wellburnt, compact and dry coal of pine or other soft wood,


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CHARCOAL. 17free from knots, and having the rings of growth as closetogether as possible. Its good quality may be known byits clear, ringing sound when struck. This should besawed into parallelepipeds six inches in length and twoin width in such a way that the rings of growth arecut oflF at right-angles to two of the long sides. Thesesides of the coal are the ones for use. The substance tobe heated is laid near the edge of the coal, sometimes ina shallow depression made in it. The other two longsides of the coal, which run parallel with the rings ofgrowth or rather with tangents to these, are unfit foruse, since in consequence of their heterogeneous struc-ture they often burn with very uneven surfacesand sometimes snap off. A substance is heated uponcoal when it is intended to reduce it, to prevent its oxid-ation, or when the unavoidable reducing effect of contactwith coal can exert no injurious influence upon the de-sired result.

2. Platinum Wire, about 0.4 of a millimeter in thick-ness, A long piece of this is bent several times aroundin the form of a ring and the free ends bent up in-to small hooks. The ring is held upon the indexfinger of the left hand, and one of the hooks, filledwith the substance to be examined, exposed to the flameof the blowpipe. Borax, or salt of phosphorus, is com-monly melted first to a transparent bead upon the hook,and then the substance to be tested, in the form of smallpieces or as a fine powder, heated with it, in order toobserve its reaction with these fluxes both in the oxi-dating and in the reducing flame. Of course, care


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18 PLATINUM AND GLASS.must be taken not to treat in this way metals or othersubstances which under such circumstances would at-tack the platinum wire.

3. Platinum Foil.This is used for fusing sub-stances which must not be subjected to any reducing-influence, as is unavoidable upon coal. The platinumfoil, which should be about 2 inches long and 1 inchwide, may be laid upon a piece of charcoal or held inforceps.

4. A Platinum Spoon, about half an inch wide.While in use the handle may be fastened to a holdermade for the purpose and furnished with a screw forsecuring it, ol* may be stuck into a cork. Such a spoonis used for melting certain substances with bisulphate ornitrate of potassa.

5. Forceps, with platinum points. Their form issuch that the two platinum points arc separated bypressing upon the heads of rivets. Between the extremi-ties of the platinum points is introduced a fragment ofthe substance to be tested before the blowpipe eitherwith reference to its fusibility or the color Avhich whenheated it imparts to the blue flame. The whole forcepsare from 5 to 6 inches long.

6. Glass Tubes, about 6 millimeters in diameter, andfrom 5 to 6 inches long. These are employed chieflyfor roasting substances containing sulphur, arsenic,selenium, tellurium or antimony, which Avhen heatedwith certain precautions in an open tube cilher depositvarious sublimates upon the inner surface of it or giveoff an odor by which they may be recognized.


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BLOWPIPE REAGENTS. 197. Glass Mattrasses, -which can be easily made by

fusing together one end of a glass tube. Their lengthshould be about 3 inches. They are used in heatingsubstances which contain volatile ingredients to protectthem as much as possible from the influence of the air.The volatile substance driven off is deposited, in thiscase, upon the inner surface of the tube, but not in anoxidized condition as when heated in an open tube.

D. The Blowpipe Reagents.la most blowpipe experiments the number of reagents

employed is very limited and the quantity of these re-quired very small. There are only three reagentswhich can be said to be extensively used.

1. Soda.Anhydrous carbonate of soda, which forcertain purposes must be free from sulphuric acid.Soda is used principally to assist in the reduction ofmetallic oxides and sulphides, upon charcoal, to decom-pose silicates and to determine the solubility or insolu-bihty of a substance when melted with it.

2. Borax.Purified borax freed by heat from thegreater part of its water of crystallization and pulver-ized. In using it, the red-hot hook of the platinumwire is dipped into the powder and the portion adheringto it melted in the flame of the blowpipe, and this ope-ration is repeated till the bend of the wire is filled witha globule which both hot and cold must appear per-fectly transparent and colorless. The still soft bead ofborax is the:i dipped into the powder of the substanceto be tested, so that a suitable quantity of the same ad-


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20 SPECIAL REAGENTS.heres to it, which can then be subjected to the influenceof the melted borax glass in the flame of the blowpipe.The solubility or insolubility of the assay is to be ob-served, and also the color of the bead in the oxidizing andin the reducing flame both while hot and after cooling.

3. Salt of Phosphorus, the well known double phos-phate of soda and ammonia. It cannot be melted to abead directly upon the platinum wire without difficulty,(since, so long as ammonia and water are disengaged, itdrops off easily), and must, therefore, first be freedfrom these by heating gradually upon charcoal, and thentaken upon the wire. The use is exactly like that ofborax.Besides these principal reagents, a few others are, incertain cases, employed, viz : Saltpeter, for oxidizingmelted substances. Bisulphate of Potassa, for expellingand determining certain volatile substances, (lithia,boracic acid, nitric acid, hydrochloric acid, bromine,iodine), as well as for the decomposition of titanates,tantalates and tungstates. Nitrate of Cobalt, chemi-cally pure and in solution, especially for testing foralumina, magnesia, oxide of zinc, oxide of tin, andtitanic acid, which moistened with the solution of cobaltand heated assume certain characteristic colors. Silica,for various purposes. Fluor-spar, mixed with a certainquantity of bisulphate of potassa, for detecting lithiaand boracic acid. Oxide or Oxalate of Nickel, for de-termining the presence of a large quantity of potassain salts containing at the same time soda and lithia.Oxide of Copper, for detecting chlorine, bromine and


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BLOWPIPE IMPLEMENTS, 21iodine. Tin, in the shape of foil, for assisting in thpreduction of substances dissolved in borax, or salt ofphosphorus. The hot bead, resting upon charcoal, is tobe touched with tin foil, so ihat a portion of this remainsupon it, and then heated a few seconds in as powerful areducing flame as possible. Silver, for detecting sulphurand sulphuric acid.

The blowpipe reagents may be best kept in bottles,well stopped Avith ground glass stoppers,which maybe packed in a wooden box constructed for the purpose.In traveling, means should bo adopted to prevent thestoppers from becoming loose and falling out.E. Other Articles nece=sary in assaying withTHE BLOWPIPE.

The method of using these articles, of which some arerather convenient than indispensable, requires no ex-planation. The following are, therefore, merely men-tioned : a hammer, a small anvil, a steel mortar, anagate mortar, files of various sorts, a knife, scissors, amagnet, a microscope, &c., &c.


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II.

QUALITATIVE EXAMINATION AVITil TUE BLOWPIPE.

This consists of the performance of certain operations,and the accurate observation of the resulting phenomena,from which the presence or absence of certain substancesmay be known. These operations may be undertakenmost advantageously in the following order, viz : Testof the substance to be examined, first, in a glass matrass,i. e. in a glass tube closed at one end; second, in a glasstube open at both ends ; thii'd, on charcoal ; fourth, inthe platinum forceps ; fifth, in the borax bead ; sixth,in the phosphorus bead ; seventh, with soda. After thesetgsts, it is often necessary to make some experiments forthe detection of certain substances, the presence orabsence of which could not be positively determined bythe preceding operations.

1. Test in Glass Matrass.The clean and perfectly dry matrass, containing a

small quantity of the Substance to be examined, is heatedat the lower end at first gently over the flame of aspirit lamp, and then gradually more intensely before theblowpipe, till the glass begins to soften.


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TEST IN GLASS MATRASS. ^3It is to be noticed whether anything is sublimed or vol-

atilized, as ex. gr. water, quicksilver, sulphur, selenium,tellurium, arsenic. The first three may be readily recog-nized from their well known properties. In case water issublimed, it should always be noticed whether it gives anacid or alkaline reaction with litmus paper. When organicsubstances are present, the fluid deposited on the wallsof the tube has a characteristic burnt taste and odor. Amicroscope is often necessary lo detect a small sublimateof quicksilver ; its use should indeed rarely be dispensedwith in these operations. Selenium gives a red subli_mate ; if a large quantity be present so that a thick crustis deposited, the color in tlie lower part of the tube issteel-gray. Tellurium produces a gray sublimate. Ar-senic yields a black deposit, which, when the quantity isconsiderable, has a somewhat metallic luster. It mustnot, however, be concluded, because these reactions donot appear, that these elements are not present, sincesulphur, selenium, tellurium and arsenic especiallymay occur in compounds from which they either cannot be liberated by such ignition, or at least not in apure condition. It is also to be observed that two ormore of them may be present in a compound and maybe sublimed together, by which the difficulty of recogniz-ing them is more or less increased. This is very oftenthe case with sulphur and arsenic. These sometimesgive a sublimate, which below consists of metallic arsenic,but higher up appears successively black, brown, redand yellow ; colors due to sulphide of arsenic, which ismore volatile than the metal. Oxygen and ammonia,


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24 TEST IN GLASS MATRASS.wlieu tlisengagcd from a substance by licat, may also bedetected in the matrass; the first, by introducing aburning splinter of wood ; the last, by the introductionof a strip of reddened litmus paper. Commonly, how-ever, ammonia is not given off in a pure state but com-bined with an acid, and then a white sublimate of anammoniacal ^alt is deposited. By mixing the assay withlime or soda, and then healing it in a raattrass, fiee am-monia is liberated and easily recognized. Some othersubslances. especially fluorine, chlorine, bromine, iodineand nitric acid, can be detected in the matrass ; sincethis, however, cannot in most cases Ite done by heatingthe substance under examination alone, but only by theuse of some particular reagent, the method avIH be givenin the eighth section, which treats of the performance cfspecial experiments for the detection of certain sub-stances.

It is to be observed, secondly, wlicther the substancefieated is in any way altered, ex. gr. changes its color andjierhaps in cooling resumes it, varies its form or state ofaggregation, exhibits a flash of light or phosphorescence,decrepitates, &c., &c. To treat in a special manner allsuch cases liere would occupy nmch space, and still notobviate the necessity of more exact chemical knowledge,which the skillful experimenter with the blowpipe mustalways have at command.

The test in the matrass gives in many cases, as appearsfrom the preceding, no distinct proof, but often only in-dications of the presence of substances which can bedetermined with absolute certainty only after still further


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TEST IN THE OPEN TUBE. 25experimentation. The indications are nevertheless ofimportance, and afford much assistance towards the finaldecision.

2. Test in the Open Tube.A portion of the assay finely pulverized is introduced

about a half an inch into the lube, and this graduallyheated at the place -where the substance lies. The lubeshould be held a little inclined, so that the current ofheated air passes over the assay, and upwards through theupper and longer part. In this Avay the assay is roasted,i. e. exposed to an oxidizing heat, by which various sub-stances are volatilized and rendered recognizable. Sul-phur is disengaged as sulphurous acid, which may beeasily known by its peculiar sufibcatiiig odor. Seleniumis but little oxidized, and deposits a red or steel-graysublimate, at the same time giving the very characteris-tic odor of selenium vaporresembling that of decayedhorseradisha ready and sure proof of its presence.Arsenic is volatilized as arsenious acid, antimony, as oxideof antimony and tellurium as tellurous acid, all of whichform a white sublimate. That of arsenious acid is dis-tinctly crystalline, while the others appear pulverulent.Arsenious acid and oxide of antimony can be driven for-ward by heat from the place where they have beendeposited, but in the case of tellurous acid, this takesplace only in appearance, since it fuses to small trans-parent drops, whicli may be detected sometimes by thenaked eye, though better with the aid of a microscope.

The roasting process must be carried on slowly with


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26 TEST ON CHARCOAL.a gradually increasing temperature and a good currentof air, produced by the inclination of the tube ; sinceotherwise, unoxidizod volatile substances might besublimed, and the assay fused together so as to preventfurther oxidation. To roast a substance as completely aspossible, it is necessary after heating it some minutes, togrind it in an agate mortar, and then to repeat theroasting. This alternate heating and grinding must becontinued till nothing more is sublimed.

3. Test on Charcoal.The same things are to be observed in heating on char-

coal' as in using the matrass. Especially important is itto become familiar with the color and certain other pro-perties of the incrustations which different substancesdeposit when heated on charcoal. These are more par-ticularly treated of in tlie following synopsis taken fromPlattner's "Art of Assaying with the Blowpipe."

Selenium melts easily, and gives in the oxidizingor reducing flame brown fumes, and deposits an incrus-tation which at a little distance from the assay is steel-gray, with a slight metallic luster, and at a greaterdistance, dull and dark-gray, inclining to violet. Thisincrustation is readily driven from one place to anotherby the oxidizing flame, but, if touched with the reducingflame, vanishes, coloring the flame at the moment beauti-ful ultramarine. When selenium fused on coal ,or adeposit from it, is touched with the blowpipe flame astrong odor of decayed horseradish is perceptible, due


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TEST ON CHARCOAL. 27to the gaseous, colorless oxide of selenium "which isthus produced.Tellurium melts very easily, gives oflf fumes and

deposits on the coal, not far from the assay, both in theoxidizing and in the reducing flame, tellurous acid. Thedeposit is white, with red or dark-yellow edges, and maybe driven from place to place by the oxidizing flame, butin the reducing flame vanishes, coloring the flame atthe same time green, or, when selenium is present, bluish-green.

Arsenic volatilizes without fusing, and deposits uponthe coal, in the reducing as well as in the oxidizingflame, arsenious acid. The deposit is white, in thin lay-ers, grayish, and at some distance from the place wherethe assay was laid. It is removed instantly whenmerely warmed by the blowpipe flame. If heated sud-denly in the reducing flame, it vanishes, giving the flamea feeble light-blue color. When volatilized it gives astrong alliaceous odor, which is peculiar to the suboxideof arsenic.

Antimony fuses readily, and incrusts the coal withoxide in both flames. The incrustation is white, inthin layers, bluish, and nearer the assay than that ofarsenious acid. By a gentle heat from the oxidizingflame, it may be driven from one place to another with-out coloring the flame, but, if exposed to the reducingflame it changes its positions with a slight greenish-blue color. The oxide of antimony being much less


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28 TEST ON CHARCOAL.volatile than the arscnious acid may bs easily distin-guished from it. If metallic antimony be melted oncharcoal and heated to redness, and then allowed to re-main undisturbed, it continues a long lime red-hot, and^ives off dense white fumes, which are partly depositedupon the coal, and partly around the globule of metalin wh.itc, penrly crystals. This phenomenon depends onthe fact that the red-hot fluid globule of metal absorbsoxygen fi-om the air, oxide of antimony is formed, andthus so much heat liberated as is rfecessary to keep thevery fusible antimony in a melted state for some time,till it becomes covered with crystals of the oxide.

Bismuth fuses very easily, and deposits on the coaloxide of bismuth, both in the oxidizing and in the re-ducing flame. The deposit is, while hot, dark orange-yellow, when cold, lemon-yellow, and in thin layers,bluish-white. The yellow deposit consists of pure oxideof bismuth, and the bluish-white, which is farthest fromthe assay, of carbonate of bismuth. The bismuth in-crustation is deposited a little nearer the assay than thatof antimony. It may be driven from place to place byeither flame, since the oxide is reduced on the coal at ared heat, and the metallic bismuth then volatilized andreoxidized, but does not, when heated in the reducingflame, impart to it any color.Lead melts easily, and gives the coal in either flame

an incrustation of oxide at the same distance from theassay as that of bismuth. The deposit while hot, isdark lemon-yellow, after cooling, sulphur-yellow, and in


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TEST ON CUARCOAL. 29thin layers, bluish-white. The yellow crust is pureoxide of lead, and the bluish-white, carbonate of lead.The yellow deposit when heated in the oxidizing flamechanges its place for the same reason as the oxide ofbismuth, and without coloring the fiaine ; in the reduc-ing flame it changes its position, tinting the flame withultramarine.

Thallium melts, volatilizes and deposits a brown in-crustation, coloring either flame a brilliant green.

Cadmium melts readily, takes fire in the oxidizingflame, burns with a dark-yellow flame and brown fumes,and deposits on the coal near the assay oxide of cad-mium. This exliibits its peculiar color best when com-pletely cold ; it is reddish-brown, in thin layers, orange-yellow. The deposit of oxide of cadimum may, sincethe oxide is easily reduced, be volatilized by either flame,but without imparting to it any color. Around the outeredge of the incrustation the coal sometimes exhibits pa-vonian tints.Indium fuses readily, forms in the oxidizing flame a coat-

ing brown while hot, and yellow when cold, and whichtouched with the reducing flame colors it blue.

Zinc fuses easily, takes fire in the oxidizing flame,burns with a very luminous, greenish-white flame anddense white fumes, and gives the coal an incrustation ofoxide. This is rather near the assay ; while warm, yel-low, and when completely cold, white. Heated in the


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30 TEST ON CHARCOAL.oxidizing flame it glows, but is not volatilized because itcannot be reduced by the heated coal on which it rests.Even in the reducing flame it is volatilized but slowly.

Tin melts without difficulty, and in the oxidizing flamebecomes covered with oxide, which may be removed by apuff of air ; in the reducing flame the fused metal pre-sents a brilliant surface and incrusts the coal with oxide.The incrustation is while hot, slightly yellow, and some-what luminous in the oxidizing flame ; but, upon cooling,it becomes white. It is so near the assay as to touch iton all sides. It cannot be volatilized.

Molybdenum, in metallic form, cannot be fusedbefore the blowpipe, but when heated in the exteriorflame gradually oxidizes, and covers the coal, at a littledistance from the assay, with molybdic acid, which isdeposited in some places, especially nearest the assay, intransparent, crystalline scales, but elsewhere in a pulveru-lent form. The deposit has while hot, a yellowish color,but on cooling becomes white. , The crystalline scalesare best produced, by heating the assay as far as possiblefrom the point of the blue flame. The pulverulent mo-lybdic acid can be driven about by either flame, but theplace which it leaves appears, after it is completely cold,dark copper red and has a metallic luster, from oxideof molybdenum, which is formed by the reducing effectof the coal on the acid, and which is not volatile. Iiithe reducing flame, metallic molybdenum remains un-changed.


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TEST ON CHARCOAL. 31Silver, held for sometime in a fluid condition by a pow-

erful oxidizing flame, gives a very slight deposit of darkred oxide. In combination -with a small quantity of lead,there appears, first, a yellow deposit of oxide of lead, butafterwards, when the silver contains less lead, it colorsthe coal outside the yellow crust dark red. If thesilver contain a little antimony, there appears, first, awhite incrustation of oxide of antimony, which, if theblowing be continued, becomes red. An alloy of silver,lead and antimony gives, after the latter metals are mostlyvolatilized, a copious, carmine red deposit. Such adeposit may also sometimes be obtained by heating aloneon charcoal a rich ore of silver.

Sulphides, Chlorides, Bromides, and Iodides ofTHE Metals.In assaying with the blowpipe, not onlyare pure metals found, which being somewhat volatile, maybe detected by the incrustation which they give the coalwhen sublimed, but there are also compounds whichdeposit a white crust upon the coal, that may be drivenoff by the oxidating flame, and very often resemblesclosely a deposit of oxide of antimony. Here belong ofthe sulphides, those of potassium and sodium, whichwhile forming from the sulphates in the reducing flameon coal, yield a white, and not very volatile incri^stationof sulphates, produced by the reoxidation of the volatil-ized sulphides. This, however, does not occur till thesulphates have sunk into the coal, and given off theiroxygen. Sulphides of potassium being more volatilethan sulphides of sodium, the former are deposited earlier,and in greater quantity than the latter. This deposit,


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82 TEST ON CUARCOAL.when touched by the reducing flame, disappears, impart-ing to the flame, when consisting of sulphate of potassa,a bluish violet color, and, when of sulphate of soda, areddish yellow. Sulphide of lithium, formed by thereduction of sulphate of lithia on coal, is also volatilizedby an intense heat, but more difficultly than sulphide ofsodium, and gives, instead of a pure white, a greenishwhite, thin crust, which touched with the reducing flamevanishes, coloring the flame caimine red. The sulphidesof lead and bitmuth also belong here. Each of thesesulphides, both in the oxidizing and the reducing flame,affords two diflfereiit deposits of whicli the most volatileis white, and is a sulphate. When these deposits areheated in the reducing flame, that of lead disappears,communicating a blue tinge to the flame ; that ofbismuth vanishes, but does not color the flame. Theincrustation nearest the assay consists of the oxide of themetal, and may be recognized from its color, both whilehot and after cooling. There are indeed several othersulphides of metals which incrust the coal, when thor-oughly heated before the blowpipe, with a more or lessabundant white deposit, ex. gr. sulphide of antimony,sulphide of zinc and sulphide of tin ; but the depositconsists only of the oxides, and is in the oxydating flameeither volatile or fixed.Among the chlorides of the metals, several possess the

property, when heated before the blowpipe on coal, ofvolatilizing and depositing a white incrustation, vizthe chlorides of potassium, sodium and lithium, aftersinking into the coal in a fluid state, volatilize and give


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TEST ON CHARCOAL. 33a white deposit near the assay, (chloride of potassiumyields the most abundant, and chloride of lithium theleast, which also instead of being pure white, is grayish) ;chlorides of ammonium, quicksilver and antimony,which volatilize without melting ; chlorides of zinc,cadmium, lead, bismuth and tin, which first melt andthen afford two incrustations, viz : a white, volatile oneof chloride, and a less volatile one of oxide. These inthe reducing flame disappear, a part of them with a col-ored flame. That of chloride of potassium is bluish, in-clining to violet, and that of chloride of sodium, reddish-yellow, of chloride of lithium, carmine red, and that ofchloride of lead, blue ; the remainder do not color thefl ime. Chloride of copper fuses and colors the flameintense ultramarine. If the blowing be long continued,it may be observed that one part of the assay is volatil-ized with white fumes having a strong odor of chlo-rine, and another deposits on the coal three rings ofdifferent colors, of which the one nearest the assay isdark-gray, the next dark-yellow to brown, and the thirdbluish-white. In the reducing flame a portion of thesemay be made to change position, coloring the flame atthe same time ultramarine.Of the bromides and iodides of metals which appear

, on coal very similar to the chlorides, should be particu-larly noticed here the bromides and iodides of potassiumand sodium. These melt and arc absorbed by the coal,and are then volatilized with white fumes, a part ofwhich formy at some distance from the assay a whitecrust on the charcoal. This when touched with the re-


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34 TEST IN FORCEPS.ducing flame disappears, the bromide and iodide of po-tassium coloring the flame bluish, inclining to violet, andbromide and iodide of sodium, reddish-jellow.

4. Test in the Platinum Forceps.It having been settled by previous experiments that

the assajr docs not vfhan heated attack platinum, a smallfragment or splinter is taken in the forceps and exposedto the point of the exterior flame. Substances -whichattack platinum may be heated on coal, or, if easily fusi-ble, on the platinum wire. The object is not only todetermine the fusibility of the assay, but also the pres-ence of certain substances which under these circum-stances impart more or less distinctly a color to the blueflame of the blowpipe. Some substances impart a yel-low, others a violet, carmine red, green, or blue color.Plattner, in bis work previously quoted, gives on thissubject the following particulars :Yellow.Soda and its salts, when fused on the plat-

inum wire in the point of the blue flame, possess theproperty of incrpasing the size of the exterior flame,and coloring it intense reddish-yellow. This reaction isnot prevented by the presence of a large quantity ofother salts, whose bases also color the exterior flame,though not so intensely as soda. For the appearance oncoal, see page 32. If a small splinter of a silicate con-taining soda be igniti-d or fused in the point of the blueflame, it increases more or less the outer flame, accordingas it is more or less fusible and contains more or less


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TEST IN FORCEPS. 35i-oda, tinging it at the same time reddish-yellow. Ifthe blowino' be long continued, this color remains un-chan'^ed, or becomRS more intense.

Violet.Potassa, Caesia and Rubidia, and most oftheir salts, except the borate and phosphate, whenfused in the point of the blue flame, color the exteriorflame distinctly violet. If, however, the salt be mixedwith only a very minute quantity of a salt of soda, thereaction is so changed tliat while near the assay a slightviolet tinge may be perceived, further from it appearsthe intense reddish-yellow of the soda. It' the mixturecontain several per cent, of a salt of soda, the reac-tion of potassa is wholly suppressed, and only that ofsoda can be perceived. The reaction of potassa is alsoiprevented by the presence] of a small quantity of a saltof lithia. For the appearance of some salts of lithia oncoal, see page 82. Many minerals containing lithia and fusible in the

point of the blue flame communicate a red color to theexterior flame. This is especially true of the micas fromAltenberg and Zinnwald, wliicli color the outer flamevery strongly ; this color diminishes, however, in inten-sity, as soon as the thin strip is melted to such an extentthat it can no longer^, be kept perfectly fluid in the flameof the blowpipe. There are also minerals which givealong with the red of lithia still another color, and insuch a manner that both appear either separate ormixed. If, for instance, a minute quantity of pulverizedtriphyline, (phosphate of lithia, iron and maganese), be


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36 TEST IN FORCEPS.fused on the platinum wire in the blue flame, thereappears in the outer flame a carmine-red streak fromlithia, surrounded by a green flame resulting from thephosphoric acid. In the forceps this is difficult toobserve because the triphjline is too easily fused. If asmall piece of amblygonitc from Cursdorf, which consistschiefly of phosphates of lithia and alumina, be fused inthe forceps in the point of the blue flame, there appearsin the exterior flame a yellowi^^h-rcd streak, which issuri'ounded by a reddish-yellow flame resulting from thepresence of soda. This color continues as long as aportion of the assay is kept in a fluid state.

Silicates containing lithia, which alone impart no redtinge to the exterior flame, do so, according to Turner,when melted with fluor-spar and bisulphate of potassa,on the platinum wire in the point of the l)lue flame, aswill be explained in section 8.

Strontia.Chloride of strontium fused on the pla-tinum wire in the point of the blue flame produces in-stantly an intense red color in the outer flame.Many other salts of strontia, ex. gr. carbonate of

strontia, (strontianite), and sulphate of strontia, (cocles-tine), when exposed to the point of the blue flame inthe forceps color the outer flame at first slightly yellow-ish, but afterwards carmine-red. The presence of barytaprevents the reaction of strontia.

Lime.Chloride of calcium tinges the exterior flamered, though not so intensely as chloride of strontium.Most pure calcites as well as massive carbonates of lime


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TEST IN FORCEPS. 37produce at first a feeble yellowish color in the exteriorflame, but afterwards when the carbonic acid is drivenoiF, a red, which is, however, less intense than that fromstrontia. The presence of baryta prevents the reac-tion of lime. Fluor spar, while fusing, colors theouter flame as deep red as calc-spar. Gypsum andanhydrite produce at first only a feeble yellowish tinge,but afterwards a rather intense red. Phosphate andborate of lime do not give a red, but a green color.Of the sihcates, none afford the reaction of hme ex-

cept table-spar, which imparts to the exterior flame aslight reddish tinge.

Green".There are seven substances which color theexterior flame green, viz : baryta, molybdic acid, oxideof copper, tellurous acid, phosphoric acid, boracic acidand thallium.

Baryta.Chloride of barium when fused on the pla-tinum wire produces in the exterior flame a green colorwhich at first appears only light-green, but afterwardsbecomes an intense yellowish-green. The color is mostbeautiful when only a very small quantity of the salt isused. Carbonate of baryta, (witherite), and sulphate ofbaryta, (heavy spar), when held in the forceps andstrongly heated in the point of the blue flame also tingethe exterior flame yellowish-green, though not so deeplyas chloride of barium. The presence of lime doesnot prevent the reaction of baryta. For instance,baryto-calcitc, consisting of carbonates of lime andbaryta, cau83s in the exterior a greenish-yellow color

3


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38 TEST IN FORCEPS.ifj however, the blowing be long continued, it may beperceived that the point of the flame is also sometimes ofa reddish tinge.MoLYBDic Acid.Molybdic acid, or oxide of molyb-

dtoum, when attached to the moistened platinum wireand ignited in the blue flame, colors the exterior flamebluish-green, exactly like baiyta, molybdic acid at thesame time volatilizing. If a thin scale of natural sul-phide of molybdenum be held by the platinum forcepsin the point of the blue flame, it does not fuse, but im-mediately imparts to the outer flame a yellowish-greentinge, resulting from the molybdic acid formed by itsoxidization.

Oxide of Copper.Oxide of copper, alone as wellas in combination with certain acids which do not them-selves give a colored flame, for instance, with carbonic,acetic, nitric and sulphuric acids, communicates to theexterior flame an emerald-green color. Metallic cop-per, when heated on *.oal in the flame of the blowpipe,is easily oxidized, and then tinges the outer flame emer-ald-green. The iodide of copper causes also a very in-tense emerald-green color in the exterior flame. Ores oflead containing copper color the outer flame in the cen-ter blue from the lead, (see below), and upon the out-side, especially near the point, emerald-green. Sili-cates containing copper, when heated in the forceps withthe point of the blue flame, sometimes impart to the exte-rior flame a very intense emerald-green color, ex. gr.dioptase, and chrysocolla.


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TEST IN FORCEPS. 39This color is also produced bj those in which the oxide

of copper constitutes an unessential, and only the col-oring part of tlie mineral, ex. gr. turquoise.Tellurous Acid.Tcllurous acid, suspended on th

moistened platinum wire, and heated in tlic point of theblue flame, melts, gives off fumes and colors the exteriorflame gre3n. If the tellurous acid, deposited on coalfrom heating an ore of tellurium, be touched with thepoint of the blue flame, it vanishes with a green, orwhen selenium is present, Avith a bluish green flame.

Phosphoric Acid.According to Fuchs and Erd-mann, phosphoric acid, phosphates and minerals contain-ing phosphoric acid, sometimes alone, and sometimesafter being pulverized and moistened with sulphuric acid,impart to the exterior flame a bluish green color. Thisreaction is so reliable that with suitable care very minutequantities of phosphoric acid may be detected in miner-als, when a little of the paste, formed by moisteningthe powder of the mineral with sulphuric acid, is takenon the platinum wire and exposed to the point of theblue flame. The same is true also of compounds, whichfrom containing a large admixture of soda or other in-tensely coloring substance, do not alone give the reac-tion of phosphoric acid. If the salt contain water,it must first be driven off by heating on coal before theblowpipe, and then the anhydrous substance pulverized,moistened with sulphuric acid, and exposed to the blueflame on the platinum wire. If soda be present, theouter flame is tinged very distinctly bluish green at the


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40 TEST IN FORCEPS.moment the phosphoric acid is liberated by the action ofthe sulphuric acid, but afterwards assumes the intensereddish yellow of tlie soda. As the bluish green lastsin some cases but a short time, it must be observedTvhether the outer flame is colored bluish green or not, atthe instant the assay is touched with the point of theblue flame. Phosphate of lead as well as pj'romorphite,heated alone, tinges the edges of the blue flame of oxideof lead with a permanent green.

BoRACic Acid.Both natural and artificial boracicacid, when melted on the platinum wire in the pointof the blue flame, impart to it a deep yellowish green,(siskin-gieen.) If, however, the acid be not perfectly freefrom soda, there results in the outer flame a green color,which is more or less mixed with yclbw. Borax aloneproduces no green, but only the yellow of soda. Anhy-drous borax, however, when pulverized and moistenedwith sulphuric acid, and exposed to the point of the blueflams, gives for a short time an intense green, whichchanges to yellow as sooiv as the suit is decomposed andthe free sulphuric acid expelled. Minerals containingboracic acid, when heated on the platinum wire withthe point of the blue flame, after being pulverized andmoistened with sulplmric acid, almost all communi-cate to the exterior flume a green color. Another andvery reliable method of detecting boracic acid in miner-als from the siskin green color of the outer flame hasbeen proposed by Turner, and will be found in section 8.Thallium.Substances containing thallium, when


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TEST IN FORCEPS. 41Strongly heated, color the flame bright green, which ischanged to yellow and thus obscarcd by the presence ofmuch soda.

Blue.There are some substances which when igni-ted or fused in the inner flame, color the exterior flameblue, viz: arsenic, antimony, lead, indium, seleniumand compounds of copper with chlorine and iodine.

Arsenic.Metallic arsenic and .the arsenides ofthose metals which do not communicate any color tothe exterior flame, as ex. gr. copper-nickel, cabaltine,&c., &c., when heated by the blue flame on coal, aresurrounded by a blaze of a light blue color. If theincrustation of arsenious acid deposited on the charcoalbe touched suddenly by the blue flame, it being veryvolatile may bo distinctly observed to disappear with thesame light blue blaze. When arseniates whose basesimpart no color to the exterior flame, as ex. gr. nickelbloom, cobalt bloom, iron sinter, &c., arc exposed inthe forceps to tlie blue flame, they communicate an in-tense light blue to the outer flame. In many cases ablue color appears even when the base possesses theproperty of coloring the flame, as ex. gr. arseniate oflime, (pharmacolite,)Antimony. When metallic antimony is fused within

the blue^flame on charcoal, the fluid globule of metal issurrounded by a scarcely perceptible blue blaze ; but,if the resulting white crust of oxide of antimony betouched with the blue flame of the blowpipe, it disap-pears tinging the flame greenish blue.


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42 TEST IN THE BORAX BEAD.Lead.When metallic lead is melted on coal within

the blue flame, the fluid metal is surrounded by a blazeof an ultramarine color, and the coal is incrusted withoxide of lead. The oxide of lead may be driven by theblue flame from one place to another, tinging the flameat the same lime with blue. Salts of lead, whose acidsdo not themselves impart a deep color to the exteriorflame, communicate to this an intense ultramarine, whenfused with the point of the blue flame, either on theplatinum wire or in the forceps.

Indium.Compounds of indium color the flame blue.Selenium.If selenium be molted on coal in the blue

flame, it volatilizes, coloring the flame intense ultra-marine. A deposit of selenium on charcoal presentsthe same appearance in the reducing flame.

Chloride of Copper.Natural or artificial chlorideof copper, ignited on the platinum wire in the blue flame,tinges the external flame at first intense ultramarine, butafterwards green from the oxide of copper formed.Bromide of Copper.Bromide of copper, treated

in the same way as the chloride, colors the flame at firstgreenish blue, but afterwards imparts the green of oxideof copper.

5. Test in the Borax Bead.Since this test serves especially to detect the oxides of

metals, it is of the first importance that, if the substanceto be examined contain unoxidized metals, it i-hould beroasted to oxidize them Metals combined with sulphur,arsenic, &c., are not only difficultly soluble in borax, but


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TEST IN THE PHOSPHORUS BEAD. 43present appearances differing more or less from those ofthe oxides. The roasting of the pulverized substancemay be performed on coal or in a glass tube. It mustbe repeated several times to produce the most completeoxidation and volatilize perfectly sulphur, arsenic, etc.Before every new roasting the substance must be groundin an agate mortar. Sulphides and arsenides of metalsmay be advantageously subjected to alternate oxidatingand reducing roastings. The latter are effected by mix-ing the pulverized assay with coal or plumbago powder,and then heating it in a glass tube or on charcoal. Thesame directions apply to the next test.

6. Test in the Phosphorus Bead.In this case, as in the preceding, it is important to

observe accurately the colors which the beads presentwhile hot, while cooling, and when cold, both in theoxidizing and reducing flames. Beads, in which certainsubstances are dissolved, possess the property of becom-ing cloudy or opaque, when treated with an intermit-tent flame. This process is called flaming. The sameresult may also generally be produced by a slow andgentle heating of the previously cooled bead. Thecloudiness of the bead is also often caused merely by theaddition of a larger quantity of the assay.


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44TABLE I.

1. Oxidizing Flame. A. Borax.

Colors of Substances which Exhibit thesk Colors.TDK Beads. In the Hot Bead. In the Cold Bead.

Silica, Silica,Alumina. Alumina.Oxide of Tin, Oxido of Tin,Tellurous Acid, ,Baryta, s^Strontia, Is"= a Tellurous Acid,Lime, Baryta,Magnesia, "1- Strontia,Colorless. Gluoioa, Lime,Yttria. s a Mas;nesia, ~A^Zirconia, -: Glucina, SaTlioria,Oxide of Lanthanum, ;? Yttria,Zirconia, 1Oxide of Silver, Thoria, 3Columbic Acid, Oxide of Lanthanum, ^S.Niobio Acid, Oxide of Silver,Columbio Acid,Niobic Acid, ^1~^Titanic Acid,


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45TABLE ICONTINUED.

1. Oxidizing Flame. A. Borax.

Colors of Substances which exhibit these Coloks.THE Beads In the Hot Bead. In the Cold Bead.

Red, yellow,or purple.

Oxido of Corium, (red).Oxifloof Iron, (dark red),Oxido of Uriniuin, (red),Viinadio Acid, (yellow),Oxide of Chromium,(dark-red),

Oxido of Corium, (by flaming,eniimel-white).Oxide of Iron, (yellow).Oxido of Uranium, (by fla-ming, cnamfl-yellow).Vanadic Acid, (yellow).Oxido of Nickel, (reddishbrown).Oxido of Manganese, (red,inclined to violet).

Color ofAmethyst. Oxide of Nickel,Oxide of Manijanese,Oxido of Didymium. Oxido of Didymium.

Blue. Oxide of Cobalt.Oxide of Cobalt,Oxido of Copper, (bluo togreenish-blue).

Green. Oxide of Copper. Oxide of Chromium, (inclinedto yellow).


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46TABLE LCONTINUED.

2. Reducing Flame. A. Borax.

Colors of Substances which exhibit these Coloes.THE Beads. In the Hot Bead. In the Cold Bead.

Silica,Alumina,Oxide of Tin,Baryta,Strontia,Lime.Maginesia,Uluclna,Yttria,Zirconia,Thoria,Oxide of Lanthanum,Oxide of Ceriutn,Columbic Acid,Oxide of Didymium,Oxide of Manjâncse.Niobic Acid, in small quantity.

Silica,Alumina,Oxide of Tin.

Colorless.

Baryta, .^-^-nStrontia, 51Lime, 0,Ma:;nesia, g^^tilucina, q 3Yttria, 1 J-Zirconia, "i?Thoria, Oxide of Lanthanum, * g*Oxide of Cerium, ofColumbic Acid. ^^^^

Oxide of I'idymium,Oxide of Manganese.

Niobic Acid, tn small quantity.

Oxide of Silver, 5"Oxide of Zinc, ^ S"Oxide of Cadmium, "^ .Ôxide of Indium, goOxide of Lead, Oxide of Thallium, s gOxide of Bismutli, sOxide of Antimony, ^^ S.Oxide of Nickel, 2 g;Tellurous Acid, *? S"

Oxide of Silver, sl*Oxide of Zinc, 1^ |-Oxide of Cadmium, ^ nOxide of Indium, 5Ôxide of Lead. J Oxide of Thallium, S S:O.tule of Bismuth, SgOxide of Antimony, 5 Oxide ol Nicliel, 2 S:Tellurous Acid. f: S*

S

Yellow tohrowH.Titanic Acid,Tuuiistic Acid,Molyt>dic Acid,Vanadic Acid.

Titanic Acid,Tungstic Acid,Molybdic Acid.

Blue. Oxide of Cobalt. Oxide of Cobalt,Titanic Acid. { f^^^J.


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47TABLE LCONTINUED.

2,REDuciNa Flame. A, Borax.Colors or Substances which exhibit these Colors.THE Beads. In the Hot Bead. In the Cold Bead.

Green.Oxide of Iron,Oxide of Uranium,Oxide of Chromium,

Oxide of Iron, (hottle-green).Oxide of Uranium, "Oxide of Chromium, (emerald-green).Vanadio Acid, (emerald-green).

Gray andcloudy.{The cloudi-ness oft e nappeas first

distinctlyduring the

Ox'de of Silver, |: *Oxifle of Zinc, ^ g.Oxide of Cadmium, S 2:Oxide of Lead, 5 ~Oxide of Bismuth, n s'SOxide cf Antimony, S.** S.Oxide of Niclvcl, .- sTellurous Acid. S M fa.

Oxide of Silver, S >Oxide of Zioc, !? g.Oxide of Cadmium, g|Oxide of Lead, S JOxide of Bismuth, o 3'3Oxide of Antimony, S." S.Oxide of Nicl


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48TABLE I.CONTINUED.

1. Oxidizing Flame. B.Salt of Phosphorus.Colors of Substances wnicn exhibit these CoLons.THE Beads. In the Hot Bead. In the Cold Bead.

Silica, (I'ery little soluble.) Silica, {very little soluble.)Alumina. /^-^^ Aluiuina.Oxule ol' Tin, h Oxide ofTin,Tellurous Acid, e Tellurous Acid,Baryta. sStrontia, S'Lime. So Baryta, .Mav.ncsia, '?l Strontia,

ifGlucina, Lime,Yttria, A Maine sia.Zirconia, n Ulucina, ol.Thoria. s Yttria, "9 aOxido of T-anthanum, V^V^ Zirconia, I'fiWiobic Acid. Tlioria, SI.Colorless. Oxide of Lanthanum,Oxido of Cerium. S"'Columbic Acid,

=0 -^Niobic Acid,Titanic Acid. Columbic Acid,Tun^stic Acid, at S Titanic Acid.Oxide of Zinc, re -- =S Tuu;iStic Acid,Oxide of Ciidinium, ^ Oxide of Zinc,Oxidu of Indium, ? c ? O.Nido of Cadmium,Oxide of I-cad, Oxido of Indium,Oxide of Tlinllmm, 5-3 Oxido of Lead.Oxide of Bismuth, S-2- Oxide of TItallium,Oxide of Antimony. ^^ Oxide of Uiginuth,Oxido of Antimony.

Columbic Acid, ^Titanic Acid,Tunjistic Acid, 5Oxido of Zinc,Oxide of Cadmium,

Oxide of Lead, c Oxide of Silver,Oxide of IJismuth, s Oxidn of Iron,Tellow, red- Oxide of Antimony. 57" Oxido of Nickel,

dish yellow V^V*. Oxido of Uranium, {ycllngreewshto red and n).reddish Oxido of Silver, Vanadic Acid,itrown. Oxid'jof Cerium,Oxide of Iron.Oxuh' of Nicljel,

Oxl.'p of Uranium.Vaoadic Acid,Oxido of Ciiromium.


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'49

TABLE I.CONTINUED.1. Oxidizing Flame. B.Salt of PnosPHORUS.Colors of SUBSTANCES WHICH EXHIBIT THESE COLORS.THE Beads In the Hot Bead. In the Cold Bead.

Color ofAmethyst. Oxirte of ivran.iranee,Oxide of Didyinium.Oxide of Marisranese,Oxide of Bidymium.

Blue. Oxido of Cobalt, Oxido of Cobalt,Oxide of Copper, (.to greenishblue.)

Green.Oxide of Copper,Molybdic Acid, (yellowish green

Molybdic Acid, (slight yellow-ish gre'^n).Oxido of Uranium, (yellowishgreen).Oxide of Chromium, {emeraldgreen).


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2. Reducing Flame. B.Salt of Phosphorus.Colors ofTHE Beads.

Colorless.

Yellow tob'ood-redmnd brown.

StTBSTANCES WHICH EXHIBIT THESE COLORS.In the Hot Bead.

Silica, Ivenj little soluble).AlaiiiinaOxide of Tin,Haryta,Stroutia,LiiDO,Magnesia,Uluuiua,Yttria.Zirconia,Tlioria,Oxiilc (if Lanthanum,Oxide of Cerium,C'llimibic Acid.Oxide of Didymiura,UxiUe of Mau;;aneso.

Oxide of Silver,Oxide of Zinc,Oxi


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2. Reducing Flame. B.Salt of Phosphorus.Colors of Substances which exhibit these Colors.THE Beads. In the Hot Bead. In the Cold Bead.

Violet. Niobic Acid (in large quantity). Niobic Acid, (in large quantity.)TiUnio Acid.

Blue.Oxido of Cobalt,Tun^stic AcidNiobic Acid, {in very large quan-

tity )

Oxido of Cobalt,Tuny:.tic Acid,Niobic Acid, (in very large quan-

tity.)

Green. Oxide of Uranium,Molybdic Acid.Oxide of Uranium,Molybdic Acid..Vanadic Acid,Oxide of Chromium,

Gray andcloudy.(The cloudi-

vess oftenappears firstdistinct ywhile thebead is cool-

ing).

Oxide of Silver,Oxide of Zinc,Oxide of Cadmium.Oxido of Lead,Oxido of Bismuth,Oxide of Antimony,Oxide of Niclicl,Tellurous Acid.

Red to red-dish andcloudy.

Oxide of Copper. Osido of Copper.


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52TABLE II.BEHAVIOR OF THE METAL-

Metallic Oxides inAlphabetic Order. On Charcoal alone. With Carbonate of Soda

1. Antimoni-ous Acid.

OFl : It is displacedwithout change, and de-posited upon another partof the Ch.

Rf'l . It is reduced andvolatilized. A Ct of an-tinionious acid is deposit-ed on the Ch, and a green-ish blue color impartedto the flame.

On Ch very readily re-duced in OFl and RFl.Tlio metal fumes and coatsthe Ch with antimoniousacid.

2. ArseniousAcid. Volatile below rod heat.

On Ch reduced, withemission of arsenicalfumes, which are charac-terized by a strong garlicodor.

3. TeroxideOF Bismuth.

OFl -. On platinum foilit fuses rea; the Ch with yellowoxide. The Ct, whentouched with tiie RFl,disaijpears without color-ing the flame.

Easily reduced to me-tallic bismuth.

4. Oxide ofCadmium.

OFl: On platinum foilunchanged.RFl : On Ch it disap-pears in a short time anddeposits all over the Cha (talk yellow or reddishbrown powder; the col-or can only 1)0 clearlydiscerned after cooling.

OFl: Insoluble.RFl : On Ch readily re-duced ; tlio metal v.ipor-ize.s and deposits a darkvcUow or reddish brownCt on the Ch.


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53Lie OXIDES BEFORE THE BLOWPIPE.

mth Bx on Platinum Wire. With S Ph on Platinum Wire.

OFL: Dissolves in lars;o quanti-ties t


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54TABLE ILCON-

Mttallir. Oxides inAlphabetical Order. On Charcoal alone. With Carbonate of Soda.

5. Sesquiox-IDE OF Ce-rium. Not changed.

Insoluble. TheSdpa'sesinto tlie th ; the Scsquiox-ide is redueeil to protoxidewiiieh remains on tlie Chas a liglit gray powder.

6. Sesquiox-ide of guro-

MIUM.Not changed.

OFI: On platinum wiresoluble to a dark yellowishl)rown ^Ihss, wliicli uncool-ini; becomes opiique andyellow.

Rl' 1 ; The glass becomesopaque ami sreen on cool-ing On C'h it eannot bereduced to metal; ilie Sdpasses into tlie Ch. and theoxide remains behind as nL'reen powder.

7. Oxide ofCobalt.

OFr: NotcTianscd.IIFI : It is re'iuced to

inetiit, but does not fusu:the mass is attnieted l>.v tiieiua;;net, and, hy iriotioii,assumes metallic lustre.

OKI : On platinum wire avery Jmall quantity is dis-fiolved to a trantiparentuKijs of a pale rediii?h oJ-or, wli'.ch (.n cooling b>c'lines ^rayKl'l: On Ch reduced to agray magnetic powder.

8. Oxide" OFCopper.

OFI : Fuses to a Mnckxlohule. wliich becomes re. I lined where it is in contactwitli the t'h.KFI: Reduced to metalat a temperature below thtineltinu; point of coppervViien the heat is increasedisrlobule of metallic cop-per isobtalucd.

OFI : On platinum wiresoluble to a lim^i 1 glass ofireen cidor-, on cooling itbecomes opuque and white.riKl : On Oh easily re-duced to metal, which whenthe teinpcrnture is buIII-conlly hi;:h f liea to one oimore globules.


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TINUED.55

JTith Bx on Platinum JT.re.OKI : Soluble to a limpid glass of

darl< yellinv or red color, which-cliiinsics on coolin'4 to yellow. Wlien)il>;lily saturated with oxid^ ttie 4'l:ui.-becoincd mi ooulin;;; enamel white.

IlFl: Tne ycllovr jjiasd hecouie.-colorie;!!*. A liiijtily gaturiitc v ir û-Thet-lass appears pure smalt-blud OFl : As with Bx, hut for the sameJiot Snd cold. An esce.ss of oxidHllu^nt^y,"' "-'"'1 *^ '^^*>^ " "ôîmparts to the head a deep bluisu;i",i'',^,'''"'*''-''^-^,black color. ' ^^^- Asm OFl.RFl: Asia OFl.

OFl : A small addition of oxide|makes the irhiis appear green wliileliot, but blua when cold. A liirgt-'quantity imparts to it a very deep OFl : As with Bx. but for the same

t>n, becomes on cooling brownish red; oooiin^.and opaque.


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66Table II.CON-

MetaUie Oxides inAlphabetical Order.

9. Teroxide'OF Gold.

On Charcoal alone.VVIien lieateil to i;;nitii)n

IFith Carbonate of Soda.Does not, fii!'>()lve in tlie

10. Oxide ofIndium.

11. Sesquiox-IDE OF Iron.

12, BiNOXIDEOF Iridium.

13. Oxide ofLead.

It becomes red uci'il lo inct Sd, but ! easily reduced,al in OKI :ind RKl. The in hoth flames, the uieUImetal Juscs easily to ii'lnC8 readily to a "iloliiile-li.t.ule. Tlito Sd piu'.-'es into the CliRKl : Is reduced and forin8a yellow l, .and when RFl : Is reduced to softstnm^ly heated colors tlic,n)etttIlioglobule8, likclcadtiame intens'e I'lui*.

OFl : Not clianjred.}kFl : ISecomes black anduia


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TINUED.57

frith Ba n Platinum IVire.

As with Carbonate of Soda.

Bead oolorless, after flainini; ;;rayand opquo. Bead colorless, turns gray whentin u added.

OFl: A small amount of oxidtcauses the jjhiss to look i'ellowwltile hot, colorless, when colil -When more oC tlio oxide is presentthe gla^s, while hot, appears re;er ad Jiiioi:of oxide causes the head to becominaine'-yellow, on cooling,RH : The ^lass diffuses itself ovcithe Ch and hecouies cloudy. Witlcontinued blowiii;^ tlin o.xide i;reduced to metal, with cfferv-csiiDce, and tho glass becomes cleaiagain.

With S Ph on Platinum Wire.

As with Carbonate of Soda.

Obi. When at a certain uuiut uf


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68TABLE ILCON-

Metallic Oxides inAlphabetical Order, On Charcoal alone.

OFl:14. Sesquiox-1|- ,/;-;;IDE OF MaN-

In soluble.r\turo

When1 suffi-

With Carbonate ofSoda.

OFl : On platinum wireor foil a very huiall quan-tity dissolves to trans-parent screen mass, wliicli

)i l)iitli the Hu^- on Cooling bccom'is opaque((Uioxido iind tliK puroxide and Iduisli sjieen

GANESE.

15, Protox-ide OF Mer-

cury.

16. molybdicAcid.

ail! converted into a reddishbrown |)owder.IIFI ; Tue same effect

Ir.stantlyvolatilized.

reduced and

RFl : On Cli it cannot bereduco


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59TINUED.

ff'itli Bx on Platinum Wire

OFl: Ciilors very intensively. Theglass, wlitlu Imt, is viule';. on coollii;:;it ussumes a roddisli tiB:;e Whenmue!i iiiiinsiancso is adJed, th' u:ia-i?iej quite black and opaque:but the color can be seen when tliuirlass. Willie solt, is tlatcencd witli theIb'ceps.RKl : Tlio slass becomes colorless.If tlie color wa.s very dark, the phe-nomenon 13 best observed uu Ch withaddiiion ot tin.

With a Ph on Platinum Wirt.OFl: A considerable addition ofman>;anesc must be luadv tu producea colored ;;lass; it tiien appears,

vliile liot, browinsli violet, andredili.-'h violet when cold, but neveropaque. ]f tlio ^lass contiiins so.small .a quantity of inau;^anese thatIt appears colorless, an addition ofnitre will produce the c'iarac:eristiecoloration

IRFl: Becomes very soon color-

ile^s.

OFl: Dissolved in large quanti-ties to a limpid l, but when cold almost colorless.Oil Ch the gla.ss becomes verydark, and on coolinj; assumes abeautiful i^reen color.UFl: The };lass assumes a verydarl..win": tlio minuteparticles of re'i'iced metal collecttogether and the ^lass bec>>inesCi>lorle.4s. This takes more readilypUccd on C.i, especially when tinIS added. The nickel then uniteswith Iho tin to a i;lot>ule.

OFl : Soluble to a reddish glasswhich, on c 'olin:, becomes yel'ow.A larger addition causes the glasito appear brownish red, while hot,and reddish yellow wlien Cold.RFl: On i'latiiiuni wire notelianj,ed. Oil Ch with tin itbecames,at first, gray and opaque; wittecontinued blowing the nickelbecomes reduced, and the glass cleara^ain and colorless.


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60TABLE II.CON-

JHetallic Oxide inAlphabetical Order.

18. BiNOXIDEOF OiMIUM.

On Charcoal alone.

19. Protox-ide OF Palla-

dium.

OFI: Cnnrerted into or.mio acid, wliicli witliout (h;-positiM'^ IV Ct. volatilizeswith its peculiar pungentodor.RFl: Ea-'ily reduced ta dark brown and infusiblemetallic powder.Reduced at a red heat:

ffit/i Carbonate of Soda.

Eifily reduced to an In-fusible metallic powder.

Insoluble: TlieSd passe?but llio metallic particles. into tlio Ch, an


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61TINUED.

With Bx on Platinum fVirt, With S Ph on Platinum Wire

OFl and RFl: Relueed, bnl not'diiuolvf^d : the metallic partlclcaunut be fused to a;{;lubule.

Like Palladium.

OPI: In part dis.--^'''' '^'^'"^ *'p-ay, hut afterwards limpia and n i-i 'V' with nxcolorless. ^^''^- A3 Wlin UX.

pnrtre.luccd. Oi cooUjis the sla&s ,. Yi Ji i i^rbecome;* opalescent cr mllkwhite.lf,^ I," ";" ,,L.lnaccording to tho amount of oxide "^h i'rt-?npresent '''"'"

OTl: Soluble to a limpid andcoloi le-s slas-t wh'ch. on Cli, becomesgrnv Irom reduced m^-talRFl : On Ch iiecomes at first ijray.afterwards colorless. The Ulibecomes coated irith tcllurous acidAs with Borax.

Glas!'. Colorless vhen saturated,opaque on cuolia^. As with Borax.

OFl : A very small quantitj'dissolves slowly to a limpid amicolorless glass, which remains soon coiilin;:.RFl : From a bi^bly saturatedgla-i-i a part of the oxide may b


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62TABLE II.CON-

Mrtallic Oxidrx inAlphabetical Ordr.r.

25. TitanicAcid.

26. tungsticAcid.

27. Sesqut-oxiDE OF Ura-

nium.

28. VanadicAcid.

On Charcoal alone. With Carbonate of Soda.

OFl : On Ch it dissolveswith cffcrvcsisence to iiiiiii'l


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63TINUED.

With Bx on Platinum Wire.

OFl : Easily soluble to a limpidelass whicii. when


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64Table IT.CON-

Metallic Oxiden inAlplutbetical Order. On Charcoal alone. With Carbonate of Soda.

OFl : When Iieated hc-^^ ^^ comes yellow and, on coolisy. Oxide OFin^, wtme u^aln. It fusesZinc. ris"' '''""" ^"^ '""' reduced "'T.\;;'n,etaURFI : is slowly reduee'I;

the reduced metal becomesrapidly re-oxiilized and theoxide deposited on anotherpart of the Ch.

OFl : InsolubleliFl : On Ch it becomesapor-

izes and coats the Ch witliwith oxide. With a power-ful flr.rae the characteristiczinc tlamo is sometimes pro-(luued


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TINUED.65

With Bx on Platinum Wire.

OFl: Dissolves readily and inlar^e quantity to a limpid ^la.svrhicli appciirs yellowish while hoton cooliti'i It is colorless. Wlienmuch of the o.\i1o is [iresent theKlUfS may 1)0 made enamel-whitehy flaminji; and on a still larjceraddition it becomes enamel white oncoolin-;.RFI: The saturated glass beoomcfat first jrray and cloudy, and finallytransparent a^ain. Un Ch theoxide heooracs reduced, the metalvaporizes and cuata the Cli withoxide.

WUh S Ph on Platinum Wirt.

As vith Borax.


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TABLE III.BEHAVIOR OF THE ALKALINEBEFORE THE

On Ch alone and in theForceps. With Carbonate of Sodaon Ck.

1. Baryta.

The Hydrate fuse*, boils,intumescex, nnd is finnlly nb-sorlied by the Cli. Tho Car-hunate fuses readily to atransparent ^las.-, which oncoiiliD^ becuaies enauiel-white. In tho forceps it col-or* the outer flame yellotriiih ;;reeD.

Fuses with Sd to a honio-jeneou3 ma.-unat fuses only at theedjjes. and svrells outin arborescent ramificationswhich eirrit a brilliant li.-;lit,and when heated witli tin;RFl impart to it a reddii^e ; sliows alter coolin;:alkaline r 'actiDii. Jn the for-ceps, colors the outer flame;purple.

8. Lime.Caustic Lime suffers

alteration. The Carbonateloses carbonic acid, bccomc.-whiter anIt beharei like Lime.

Forms an infusible com'pound, with sliu;ht intumescence. Tho excess of Sd isabsorbed by tho Ch.


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67EARTHS AND THE EARTHS PROPER,BLOWPIPE.

JFitk Bx on Platinum Wirt. With S Ph on Platinum Wire.

The Carbonate dissolves with ef-fervescPiice t a liinpiil sila-x, vliichwhi;n in a certain ."tate of Siitura-lion may he inailo opaquo hyfiatnin;;; when still more saturatedit hecotnen opaque oa cooling, evenWithuutflauiiai;.

As witli Borax.

Like Baryta. Liko Baryta.

Readily dissolved to a limpidjrliiss. wliieh heoomfS opaque hyflaming. Tlie Carlxinate dL^jjolvcswith etlerve^conce. On a lar^e aiiili-tion of L'ine the tcl'vss crystallizerton coolinK. hut does not becomeenamel-white.

Solulile in largo quantitie* to alimpid glass wliiuli, when sufiioientLime h present, becomes opaque byliuiuing. When saturated, tlio glassbecomes enamel-white un coolinj;.

It behaves lilte Lime, but does notcrystallize so well.

Readily soluble to a limpid irlass.wliich become* op.ique liy llaraing.When saturated, it becomes ou cool-ing enaml-white.

Dissolves slowly to a limpidglass, which remains so on conlin^,and wliich cannot he made cloudyby flauiinj;. A 1 ir^e quantity ofAlum'na m:ikes the };l>'*s cloudy;on cooling, it asiumes a crystalliuosurface.

Soluble to a limpid glas.^. whichremains clear unJerall circuui tiin-ces. -irtoo mucli Alumina is added,the undissolved portion becomestranslucent.


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C8Table III.CON-

6. Glucina.

7. Yttria.

8. Zircoxia

On Ch alone and in theForceps.

Not hanged.

Not chan-'od.

Infusible, but omittiDS arury bnliiaat li^bt.

ff'iih Carbonate of Sodaon Ch.

Insoluble.

Insoluble.

Insolublo.


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69TINUED.

mth Bx on Platinum Wire. With S Ph on Platinnm Wire.Soluble in lar^re quantities to alimpid jrlass, which becouies opaqueby lliiuiing When Glueina is piuF-ent in excess it becomes enamel-White ou coolinjj.

As with Borax,

Like Glucina. Like Glucina.

Like Glucina. Dissolves more slowly than withBorax.


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7. Test with Soda.The substance to be examined is pulverized, mixed

"with soda, moistened a little and spread on coal. Atfirst it should be heated gently, but aftci- (he moisture isdriven off the temperature should be raised as liigh aspossible. It should now be observed, first, -whether theassay eflfervesces, anxl fuses with the soda ; or second,whether it is reduced ; or third, whether neither one northe other occurs, in which case the melted soda sinksgradually into the coal, and the assay remains unchanged.

Silicic, titanic, tungstic and molybdic acids effervesce,and fuse with the soda. Silicic and titanic acids underthese circumstances melt to a bead. The former onlygives, (when not too much soda is employed), a beadwhich remains transparent after cooling, -while that ofthe latter becomes, in cooling, opaque and crystalline.Tungstic and molybdic acids are absorbed by the coal astungstate and molybdate of soda. It should also be no-ticed here that salts of baryta and strontia form, whenfused with soda, compounds -which are absorbed by thecoal.

All the oxides of the noble metals, as well as the ox-ides and acids of molybdenum, tungsten, antimony,


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TEST WITH SODA. 71arsenic, tellurium, copper, quicksilver, bismuth, tin, lead,zinc, cadmium, nickel, cobalt and iron are reduced oncoal with soda, when heated by the reducing flame.Arsenic and quicksilver are instantly volatilized, andsometimes leave behind a scarcely perceptible deposit onthe coal. Antimony, tellurium, bismuth, lead, thallium,zinc, cadmium and indium are partially volatilized, andform on the coal distinct incrustations. The fixedmetals, when thus reduced, are found either melted orunmelted in the soda, and arc best detected by grindingthe part of the coal into which the soda lias sunk in anagate mortar, and carefully washing off the particles ofcoal with water. Those metals which are fusible andmalleable remain in the mortar as flat pieces and scales,and the infusible and unmalleable as a powder with ametallic luster. Instead of soda, it is better, accordingto Plattner, to use with those oxides which are reducedwith diflBculty, oxalate of potassa. Soda is, moreover,employed as a special reagent for detecting manganese,especially when present in very small quantity. Whena substance containing manganese is fused on platinumfoil in the. oxidizing flame with soda, or better with amixture of soda and saltpeter, a mass is obtained whichis colored green, or when cold bluish green, by manga-nate of soda.

8. Special Tests.By the methods thus far given for assaying with the

blowpipe, it is not always possible to decide with certaintyupon all the substances which may appear, but it is often


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72 SPECIAL TESTS.necessary to undertake for this purpose still further ex-periments. These experiments, which have i'or theirobject the special determination of certain substances, orserve to confirm results previously obtained, are brieflygiven below.

PoTASSA.The presence of potassa in substances,whi ; besides this contain so much soda or lithia as toprevent its reaction on the blue flame of the blowpipe,(see Test in the Platinum Forceps), can, when thequantity is saffi3iently large, be proved by dissolving ina bead of borax, colored brownish by oxide of nickel, aportion of the assay, and observing the color of the beadwhen cold. A more or less distinct bluish tinge denotesthe presence of potassa. Since the reaction depends, ofcourse, upon the quantity of the assay in the bead, itmust be gradually increased to the required amount.The bead must be heated on the platinum wire in theoxidating flame.

LixniA.Silicates which contain only a small quantityof lithia, as, for instance, many turmalines and scapolites,either do not redden the exterior flame at all or onlyvery slightly. In this case it is" necessary to adopt themethod proposed by Turner, by which even a smallamount of lithia may be detected. The process is asfollows : The silicate is pulverized as finely as possibleand made into a paste with a mixture of one part offluor-spar with one and a half parts of bisulphate ofpotassa and a little water, and fused on the platinum wirein the blue flame, the color of the exterior flame beingcarefully noticed. According to Merlet, it is often


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SPECIAL TESTS. 73necessary in order to be positive in regard to the reactionto use two parts of the mixture with one part of thoassay. If the silicate contains a small quantity of lithia,the outer flame will be colored red, though not so brightlyas from lithia alone, the color inclining strongly to theviolet of the potassa. If the silicate be free from lithia,only the violet color of the potassa appears. If it con-tains soda, it is not always possible to obtain a distinctreaction from the lithia. If boracic acid be present inthe silicate, as in turmilino, the outer flame exhibits firsta green tinge denoting the presence of the acid, batafterwards a wine or less intense red from the lithia.Another method of detecting lithia when mixed with sodais Slid to be to dip tho assay, mDistoned with hydrochloricacid, into melted wax and then heat it in the blue flame,by which, at the first moment, a red color is prodaced.Bdracic Acid.Turner has proposed the following

method of testing for boracic acid in salts and minerals :The assay is to be pulverized as finely as possible andmade into a paste with water and a flux consisting offour and a half parts of bisalphate of potassa and onepart of fluor-spar, which is perfectly free fi'om boracicacid, and fnsed on the platinum wire in the blue flame.While the mass is fusing fluo-boracic acid is formedwhich is driven oflf and colors the exterior flame a deepyellowish green, (siskin-green.) The green color of theflame continues, however, only so long as fluo-boracicacid gas is disengiged. If, therefore, the quantity ofboracic acid be small, strict attention must be given,


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74 SPECIAL TESTS.since the color lasts only the few seconds in which thematerials of the bead are operating on each other. Ac-cording to Merlet, it is often necessary, in order to obtaina reliable result, to employ with oae part ot the assaythree or four parts of the flux.

Silicic Acid.This may be most easily detected insilicates by lieating a small splinter or fragment in a beadof salt of phosphorus. The silicic acid, being nearlyinsoluble in the salt, is separated from the soluble partsand forms a more or less transparent mass of the formof the assay used,

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Scheerer-The Blowpipe Manual