Preparation of Sal 00 Mark

7/30/2019 Preparation of Sal 00 Mark

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UNWERSJi^ V LiBEARIES


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Iat 514'Markham, J. H.iThe preparation of salicylic1 acid from phenol


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Digitized by tine Internet Arcliivein 2009 witli funding from

CARLI: Consortium of Academic and Researcli Libraries in Illinois


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The Preparation of Salicylic AcidFROM Phenol

a thesisPRESENTED BY

J. H. MARKHAM AND B. W. LEWISTO THE

PRESIDENT AND FACULTYOF

ARMOUR INSTITUTE OF TECHNOLOGYFOR THE DEGREE OF

BACHELOR OF SCIENCEIN

CHEMICAL ENGINEERING

MAY 29, 1919APPROVED

I'lnA-^scr of C(.r i.f CtKiiiicnl KiiK'iitrcrinsr

^H\C^GO. ^^ " Dran of Cultunil Sl.iilies


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I H D S XPAGE

PROBLEM 2OCGUEHENCE MD LETHODS OF PREPAHATIOil 3KOLBE'S PROCESS 7PHYSICAL PROPERTIES 10

CHEMICAL PROPERTIES 14USES 0? SALICYLIC ACID 20OUR I.IETHOD OP PREPARATIOII 25EXPSRIMEITTAL RUIIS 30PURIEICATIOE 3^

THE CHEMISTRY OE TEE SCHMIDT METHOD 36COECLUSIOH ^REEEREKCES ^^

2S1S5


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This work v;as done under the general directionand supervision of Professor Harry McCormack,for which respectful acknowledgment is herebymade.


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PROBIEI.I.

Preparation of Salicylic acid fromphenol. Using phenol as a starting substanceto prepare the acid, to study the process andto purify the product. It was originally in-tended to start v.ith tenzol and go thru thesynthesis of sodium phenate, tut since theprice of phenol has reached such a lov; price,and since the synthesis of phenol is now moreor less standard, the process starts with phenoland caustic soda.


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OCCUnRElJCE AllD LIETHODE OF PP.EPAHATIOIT

Ortho-hyuroxy-carboxylic acid, orortho-hydroxy-'bensoic acid or ortho-hydroxy-c art oxy-b eri zene

C H7 6 3C H . OH.COOH (1-2)6 4

COOHH OEH H

E

The acid v.as first discovered byH. Piria in 16S9, by fusing salicylic alde-hyde v;ith potassium hydroxide. Calhoursproved in 1843 that oil of v.intergreen ismainly methyl salicylate. In 1653 A. Ho fnanconverted anthranilic acid into salicylicacid by means of nitrous acid. Finally Ilolbeand lautemann prepared it synthetically fromphenol, sodium and carbon dioxide in 1673.


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Natural salicylic acid isfound in many plants, usually in the form ofmethyl salicylate or oil of v.inter^reen

C^H fOH)COOOII-6 4 3

The acid may be obtained from thefollowing plants: Gaulterla fragrantissima,Gaulteria procumbeus, Gaulteria punctata,Gaulterla leukocarpa, Betula lenta, Llonotropahypopitis, Spiraea ulmaria, Gloria superba andfrom many other plants. The acid is also foundin very small quantities in some grapes, strav,-berries, cherries and in fact in most fruits.

Salicylic acid may be prepared by oneof the following methods:

1. 3y oxidation of, or by fusion vfithpotassium hydroxide, or by electrolysis of oneof the following substances; salicin, salicycaldehyde, and saligenin.

2. 2y fusing potassium hydroxide withone of the following substances; benzoic acid.


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indigo, coumarin, ortho-chlor-benzoic acid, ortho-toluene Bulphonio acid , ortho-cresol-sulphonicacid, ethyl-cresol-sulphonic acid.

3. By heating with water ortho-diazo-amldobenzoic acid.

4. By dry distillation of calciutn salt ofanie acid or meta-oxybenzoic acid.

5. 3y reaction of potassium permanganateon the potassium salt of o-cresolsulphonic acid.

.6. By heating phenol with carbon tet-rachloride and alco::olic potash; p-oxybenzoicacid is here also obtained.

C H OH+CCl + 6 KOE -* C H .OZ.GOOX * ZOL *6 5 4 6 4SHgO

7. By oxidation of toluene ortho-phos-phonic acid with alkaline potassium permanganate.

8. By distillation of sodium phenyl car-bonate in a current of carton dioxide with sodiumphenate.

9. By action of nitrous acid on anthranilicacid.


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10. By electrolysis of a solution of ben-zoic acid ii) acetic acid.

11. By exposing a solution of benzoic acidto the sunlight in the presence of a ferric salt.

1, By passing dry carbon dioxide into ahot mixture of phenol and sodium.

(Kolbe and lautemann)


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KOIBE'S PROCESS.

This method has teen used for the manu-facture of salicylic acid on a large scale.

Equivalent quantities of pure phenoland a concentrated solution of sodium hydroxideare thoroughly mixed and evaporated to dryness iniron vessels with constant stirring. When themass is dry it is pulverized, placed in a metalretort and heated to 100C while a current ofheated dry carton dioxide is passed in. The massis kept well stirred and the temperature is slow-ly raised to 180G. This operation takes severalhours. After the retort has ceen heated for sometime the phenol begins to distill over. V/hen theevolution of phenol ceases, the temperature israised to 200C and the operation stopped. Whenthe mass has cooled, it is dissolved in v.ater andthe resinous substances precipitated with a miner-al acid, a further addition of acid precipitatessalicylic acid, which is then purified.

This process may be regarded as taking


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place In four stages:1. Phenol and sodium hydroxide form

sodium phenate:-C-HpOH ^ ITaOH ^ C-HÔNa * HÔ6 5 6 5 E

E. Carton dioxide when added to thesodium phenate forms sodium phenyl cartonate:-

C^HÔHa * CO^ = C^H^.OCO^.lTa6 5 E 6 5 EThis stage is completed v.hen the mass is heat-ed to about 110G for one hour.

3. The sodium phenylcartonate is trans-formed into sodium salicylate:-

C^H^.OCO^.lIa = C^H,.0H.C001Ia6 5 6 4The COg goes into the Ortho-position tetv.-eenthe hydrogen atom and the neucleus, producing acaroxyl group.

4. In the last stage the salt acts withsome unchanged sodium phenate and sets free theTDhenol in the disodium salt


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C H .OH.COOIIa-C H^.OlIa = C H .Ol^Ta.COOlIa * G H^OH64 65 64 65This change takes place during the last stage ofheating.


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physicjVI properties .

Salicylic acid crystallizes irotn ^vaterin long white needles, having a sweetish astrin-gent taste. From alcohol salicylic acid crystal-lizes in large colorless monoclinic prisms.

The acid, has a specific gravity of1.48 - 1.465 at 4^0; melting point 158 - 1593.Pure salicylic acid dried in vacuum over sulphuricacid gives a melting point of 158, 5C. Smallamounts of p-hydroxybenzoic acid lower the melt-ing point. ".Vhen slov/ly heated to 200G is sub-limes, and on cooling deposits in long fineneedles; when rapidly heated to 200C it vala-tilizes and the vapors undergo a partial dis-sociation into phenol and carton dioxide, accord-ing to the formula:

? a^ k : 254.9l-a2

7/here P^pressure in cm. of mercury,a=rdegree of dissociation. This is an irreversiblereaction.


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Heat of comTDustion of salicylic acidis 5162 cal. per gram or 754990 cal. per mole-cule. Heat of formation from phenol 5520 cal.;latent heat of futic/. - 6550 cal.; heat of neu-tralisation of a solution of the acid with l/Emolecule of sodium hydroxide 12910, and v.-ithanother half molecule .810 cal.

Salicylic acid is slightly soluble incold vvater or petroleuoi ether, hut (luite solublein hot water.

0


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The acid is very soluble in chloroform,alcohol, ether, aceton and ethyl acetate.100 parts of ether dissolve at 15 50.47 of acid100100100100100100

absolute alcohol dissolve 49.65 of acid90;'o 42.09


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Chloroform or ether remove it fromVv'ater solutions.

Salicylic acid can "be distilled insteam.

The para-acid and traces of the meta-acid usually accompany the ortno-acid if extremecare is not ohserved in preparation.


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CHEMICAL PROPiiRTIES.

Salicylic acid is both an acid and aphenol. It forms three sets of salts; acid,"basic and neutral, as well as ethers.

'.Vhen heated to 200 G it decomposesinto phenol and carbon dioxideCgK^.OH.COOH = GgHg.OH * CO^

Heated in a closed vessel with waterit decomposes into phenol and carbon dioxide at2E0-230; a similar decomposition takes placewhen treated with con. hydrochloric or hydrobromicacid, or with dil. sulphuric at 140-1500 , or withcon. phosphoric at 120.

Phosphorus trichloride gives qjI^ClPOg,which is decomposed by water into salicylic acidand phosphoric acid. When treated with phosphorouspentachloride and the products distilled, ortho-chlorbenzoylchloride is obtained. Phosphorouspentabromide yields raonobrom-salicylic acid, andthis on heating with alcohol or phenol gives the


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esters of salicj^lic acid. Phosphorous oxychloridegives on heating salicylic anhydride.

Salicylic acid or its salts give a deepviolet coloration in a neutral solution v/ith fer-ric salts. This reaction is used for qualitativeas well as quantitative determinations of sali-cylic acid. 2his test is sensitive to about1:550,000. Hov/ever phenol or salicylic aldehydegive the same test. The color is not removedhy acetic acid. This test fails, if for one partof salicylic acid there is present 365 parts ofsodium nitrate or 36 parts of sodium chloride.

Dry hot ammonia breaks up salicylicacid into phenol and carbon dioxide.

On oxidation with potassium bichromatein sulphuric acid carbon dioxide and v.ater areproduced.

Potassium chlorate and hydrochloricacid oxidize it to chloranil.

Potassium permanganate oxidizes it toformic acid and carbon dioxide.


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On oxidation witli potassium persul-phate in an alkaline solution and subsequentcolling with an acid hydroquinone carboxylicacid is obtained.

Chlorine forms mono- and di- substitu-tion products.

Dil. nitric acid forms nitro-salicylicacid, while con, nitric acid forms picric acid.

Sodium amalgam in the presence ofboric acid produces salicylic aldehyde.

On heating v/ith resorcin it gives tri-oxybenzophenone.

Sodium and amyl alcohol reduce itchiefly to pimelic acid.

Concentrated sulphuric acid gives mono-sulpho-salicylic acid.

By heating v.ith concentrated sulphuricacid and potassium ferrocaynide phthallc acid isobtained. xhe same product is obtained whensalicylic acid is heated vvith oxalic acid and

glycerin.


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Y/hen salicylic acid is heated with"butyl alcohol and zinc chloride a homologue01 the acid is obtained, which on distillationgoes into tutyl phenol.

It cotahines v^ith diazo-hodies to formazo-compounds.

nitrous acid passed into an etherialsolution of salicylic acid gives nitro- anddiaao-oxyhenzoic acids.

At 210 aiiiline gives phenol andC.H^(OH).GOIIPhH.o 4

Gyanamide and alcohol at 100 formurea and ortho-oxybenzoic ether.

Phenol and stannic chloride at 120give op-di-oxy'benzophenone,

V.'ith camphor it forms a compoundC H 02G, H 0, which melts at 50.7 6 3 10^5

On heating with soda lime phenol andcarton dioxide are formed

C^H, (OH) GO. OH Geo = C,H_OH - GaCO_6 4 o 5 o


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Potassium persulphate added to asolution of salicylic acid and potassium hy-droxide forms a crystalline compound

C H (CO K)OSO K

A solution of salicylic acid and boraxin water deposit crystals of a composition

4 10 7Chloral forms with it at 140^^

^ 4 cue 5In dilute aqueous solutions "bromine

water gives a x>recipitate of C;.Hr;Br.O, -^ -^ OctIodine and potash give a red pov.der GgH^KODCOgZ.

It forms compounds with casein,fihrim and albuminoid, containing about 14;j ofthe acid and having a foraiula *^7E^11 ^^'18^^822C H . It melts at 40, and is soluble in7 6 Swater to an extent of ,0051 parts in 100 partsof water.


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".'.Tien taken Internally it is excretedas salicyluric acid or salicyl-glycocoll


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USES 0? SAIICYLIC ACID.Salicylic acid is largely used in the

preparation of pharmaceuticals. The acid isalso of importance in the manufacture of syn-thetic chemicals, such as dye stuffs. Its chiefpharmaceutical uses are as an antirheumatic andas an antiseptic. Llany states and countriesforhid its use as a food .preservative in whichfield it formally found one of its largest uses.

The acid finds extensive use in theproduction of salicylates. V/hen ethyl alcoholand sulfuric or hydrochloric acid reacts withthe salicylic acid, ethyl salicylate results.Llethyl salicylate, oil of wintergreen may be pre-pared from methyl alcohol and the acids in thesame manner. Llethyl salicylate is extensivelyprescribed for external uses. Allyl salicylatewhich is prepared in the manner as describedabove, is used both medicinally and as a perfume.Phenyl salicylate, Salol , another derivative ofthe acid is a very important pharmaceutical; but

because of its cost, other salicylatesare sub-


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stituted. V/hen phosphorous oxychloride isallowed to react with the acid phenyl sali-cylate is thus formed. Acetyl salicylic acid,"Aspirin", is prepared from salicylic acid andacetyl chloride. "Aspirin finds extensive usein the treatment of rheumatic conditions. Allof the Salicylic preparations taken internally,are used for T;he henefit of the salicylic acidv/hich is liberated in the decomposition of thecompound. Quinine salicylate is one of thefew compounds, prepared directly from the sodiumsalt.

Among the most important salicylicsalts vi'hich are used in the preparation of anti-rheumatic compounds are: tolypyrinesalicylatesalicylic-sulfonic acid, salicylamide, salicyl-a-methyl-phenyl-hydrazone and methl-acetyl-salicylate.It is interesting to note that in the productionof the raethyl-acetyl-salicylate, anhydous zincchloride is said to act as a catalytic agent.


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The next important use of salicyio acidis in the synthesis of many important organicbodies.

The first of these "bodies to receiveconsideration is Saligenin.

CH OH (y-3)OH

This "body is prepared from salicylicacid, thru the amide, and the reduction of thelatter with sodium amalgam in acid solutiOii.

Trichlor-a-a-glyceric acid is pre-pared by the action of potassium chlorate andhydrochloric acid upon salicylic acid. V/hensalicylic acid is iodised by various methods,among our products are iouosalicylic acid, vhichon rapid heat-inr gives iodophenol, from whichcatechol can be obtained.

^^uinol, hydroq^uii'Oiie, paradihydroxy-benzene, 1-4 phendiol may be synthesized fromsalicylic acid.


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First the salicylic acid is iodisedor 'brominated so a.s to form 5 iodo- or 5 crom-salicylic acid which on fusion v/ith potashgives 2:5 dihydroxy "ceni'-oic acid. This "body ondry distillation yields quinol. This same todymay he prepared ty first nitrating the salicylicacid into the 5-nitro acid and then to the 5-amino salicylic acid, thence converting to the E-5dihydroxy"benzoic acid hy the diazo method.

llote: The 5-amino-salicylic acid is best pre-pared by the redaction of benzeneazoealicylicacid. 5-lTitrosalicylic acid on heating with limegives p- nitrophenol, -..hich can be reduced to p-amidophenol . and treated as above.

Salicylic acid yields gentisic acid bydirect oxidation with potassium persulphate inalkaline solution.

Anisic alde?iyde: p-methoxyben::oic alde-hyde

CHO

OCH


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This liOdy is found in the volatile oilfrom the wood and the bark of the Chione glabra.It cari ce prepared from salicylic acid by firstconverting to the aldehyde then thru S-methoxy-benzoylacetic ester.

Euxanthone

xhis body exists in euarthic acid orIndian Yellov.-. It is found in the free stateIn coloring matter resulting from decomposition.Upon nitration, salicylic acid yields 5-nitroand upon reduction forms 5-arainosalicylic acid.The amino- acid gives gentisic acid by the diasomethod.

There are numerous other bodies thatare prepared synthetically by means of the sali-cylic acid and its salts.


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OUR Iffi'xHOD OP PREPAHATIOH. (4th Ruii)

The materials used were pure sodiumhydroxide and crystalline phenol. 120 gransof sodium hydroxide are dissolved in an equalweight of v.ater in a porcelain dish and cooled.This is slowly added to 260 grams of phenol ina shallow enameled pan, about 14xGxl". Themixture is well stirred up and kept cool. Thisgives a mixture v/hich is only slightly colored.It is now placed in the vacuum drying chest toce evaporated to dryness. A vacuum of atout 2"is maintained and the temperature is kept downto 50-6C 2. The temperature must be just highenough so that the mass will barely boil. Thetemperature must ce kept low in ordei- to avoidcharring. This is a very essential step in theprocess.

The mass will gradually begin tothicken and in about three hours it will becompletely solid. It is now removed from thedrying chest and quickly powdered in an iron


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mortar to a fine powder. The fine material isnov/ placed back in the drying chest, tut thesteam is turned off, and it is dried for abouthalf an hour.

The pov/der thus obtained is sodiumphenate. It is pinkish Y/hite in color, somev/hathygroscopic and very soluble in vvater, acetoneor alcohol.

'.Vhen dry the sodium phenate is placedin the autoclave and the lid is put on. Theautoclave used was made of copper, about 14"tall and about 6" in diameter and about S/16"thick. The lid was furnished with a lead gasketand it formed a tight joint with the body of theautoclave. The cover had a safety valve, apassage for gas and a well for a thermometer.The lid was fastened by means of a heavy bracliet.


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Having placed the sodium phenate intothe autoclave and the lid put in place, it isnow tightly clamped in its seat. The gas inletin autoclave cover is connected by means of heavyrubber tubing to an iron pipe containing calciumchloride. This pipe is about ' long and 1" indiameter; it is filled v;ith granular calcium c'nlor-ide protected at both ends with glass v.ool andwire gauze. The other end of this pipe is con-nected to a carbon dioxide tank cy means of extraheavy rubber tubing.

The autoclave is now suspended in sucha manner, that the bottom is immersed to a depthof atout 3" in running cold water. The carbondioxide gas is turned on, the pressure in the auto-clave is not allowed to exceed 10 lbs. This iskept up for about an hour when the pressure is in-creased to 75 lbs. and at the same time the cool-ing is discontinued. V.lien no more carbon dioxideis being absorbed, the pressure is brought up to75 lbs. again and allowed to stand for about onehour.


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The cooling during the first stagesof the carhon dioxide ahsorhtion is quite adesirable feature, because the temperature tendsto rise considerably and if the mass is notcooled, phenol is split off, the mass chares andfuses together making further absorbtion diffi-cult.

A paraffin bath is nov; brought underthe autoclave so that the bottom vdll be immersedin paraffin to a depth of about 5". The temper-

ature 01 the bath is gradually raised to 120 Gand for four hours the temperature is carefullykept at 120-140C. The temperature of paraffinbath must ue taken and not the temperature inthe well in the autoclave cover. The lattertemperature is about 50 below the temperatureof the paraffin bath.

At the end of the four hours the auto-clave is allowed to cool off. V.'hen cool the auto-clave is opened, the mass is transferred to a dishand water added. The water is brought to a boiland a few o.c. of con. hydrochloric acid added.


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This throws out the tarry matter and creosoticacids. This is separated in a separatory funnel.The solution is now cooled and more hydrochloricacid added. This throws out the impure sali-cylic acid.

The impure acid is collected by fil-tration and is dried. Yield 44 gr. or 16;^ ofthe theoretical.

With some modifications this is theSohmitt method of preparation of salicylic acid.


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EZPERILffiKTAI RUKS. (1st Run)

lEO gr. of sodium hydroxide were ais-solved in an equal amount of water and mixed into260 gm. of phenol. This was evaporated at 140Cand 14" vacuum. 350 grams of sodium phenate ob-tained. This was dark hrovai in color and veryhygroscopic. The phenate was powdered up, placedin under a pressure of 10 Ihs., which was increas-ed to 50 Ihs. in the course of half an hour. Theautoclave "became very warm during the passage ofcarbon dioxide. This pressure was kept up fortwo hours, then it was removed and the contentsof the autoclave examined. The mass was dark"brown in color and of a thick pasty consistency;it smelt strongly of phenol. The cover ".vat re-placed and 50 lbs, of pressure applied from theoar'Lon dioxide tank. The autoclave was placedin a paraffin bath and heated for two hours at130-145C. During this heating the pressureinside the autoclave went up to 60 lbs.

At the end of the two hours the auto-


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clave was allov;ed to cool off, and the contentswere examined. The mass v.as of a dark brov.ncolor, moist and covered on top with fine cry-stals of phenol. This was transferred to anevaporating dish and dissolved in hot water. Alittle hydrochloric acid threw dov.Ti the tarrymatter which was separated out. The remainingpart was tested with ferric chloride after theexcess of hydrochloric acid was neutralized withcalcium cartonate. The test did not show thepresence of salicylate.


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EZPERIIJIEKTAI RUNS. (End Run)

The same amounts of phenol and sodiumhydroxide used as in the previous run. Evapor-ated at 100C and 18" vacuum.

The sodium phenate obtained was lightbrovm in color and hygroscopic. It was poudered ,placed in the autoclave and carton dioxide gaspassed in at a pressure of 10 lbs. and withinhalf an hour this was gradually increaeed to 60lbs. The autoclave became very warm. The press-ure was kept up for two hours, then removed andthe contents examined. The mass was brown incolor, moist and s;nelt of phenol. The cover wasnow replaced and 60 lbs. of pressure applied fromthe carbon dioxide tank. The autoclave was heat-ed for three hours at 150-145C. The pressurein the autoclave increased during heating to 70lbs.

At the end of the three hours the auto-clave was allowed to cool off and the mass examined,It was brown in color, somewhat moist and covered


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with crystals of phenol.This was treated as in the first run,

and the ferric chloride gave a very strong test.However, there v.as not enough salicylate presentto allow of its isolation in a oure state.


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ESPSRIMEIITAL RUUS. (Srd Run)

The same amounts of phenol tmd sodiumhydroxide used. The mixture was evaporated at60C and 22" vacuum. The sodium phenate obtain-ed v.as pinkish v.hite in color and slightly hy-groscopic.

It v.as powdered and placed in the auto-clave. Carbon dioxide gas was passed in at apressure of 5 Ihs. and the autoclave v,as cooledby means of running cold water, as descriced inRun 4. In the course of an hour the pressurewas gradually increased to 70 lbs. and kept upfor another hour. The pressure was now removedand the mass in the autoclave examined. It v.'aslight in color, dry, porous and it had a faintodor of phenol.

After the cover was replaced, 70 lbs.of pressure was applied from the caruon dioxidetank ana the autoclave heated at 120-1400G forfour hours.

After the autoclave had cooled off the


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mass was transferred to an evaporating dish. Itwas brownish gray in color, dry and had a faintodor of phenol. Hot v.-ater was added and afterthe tarry matter was separated out the impuresalicylic acid was thrown out by another addit-ion of hydrochloric acid. [This was collectedon the filter and dried. Yield 14 gr. or 4^.


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PURIi'ICATIOlI Oi' THE lUPUHE ACID.

The impure acid is dissolved in "boil-ing v.-ater and then neutralii:ed v/ith calciumoartonate and allowed to cool. Calcium sali-cylate separates oat in hard glistening crystals.A fairly pure acid yields almost pure white cry-stals, hut an impure acid gives brov.nish cry-stals. A second crystallization is ootained fromthe mother liquor.

The calcium salt is again crystallizedfrom water, until a pure white salt is ohtaiii-ed. It is now decomposed with hydrochloric acidand the pure sclicylic acid is washed with alittle cold v.ater and finally crystallized outfrom dilute aloohol. This gives a very puresalicylic acid in the form of large prismaticcrystals.

After this purification only 29 gr.of pure acid was octained. or 6.3;: of the theo-retical yield.

The chief impurities found in impure


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acid are: phenol, creosotic acid due to impurephenol, para-hydroxy-benzoic acid and a-hydroxy-Iso-phthalic acid due to the presence of causticBOda and to a too high or too low temperaturein the manufacture.

The presence of a small amount of Jm-puritiee causes the acid to crystallize fromdilute alcohol in the form of a mass of inter-laced crystals instead of well defined largeprisms.

It is quite clear that with properconditions present, the yield depends on thepressure. However, the highest pressure ob-tainahle with the equipment on hand v.as 75 lbs.per sq. in. , therefore no further runs wereattem'oted.


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TEE CH3LII'i?Ry OF THE SCffi.IITT LETHOD.

The chemistry of preparation of sali-cylic acid by the method proposed by Schinittwas explained by S. Tijmstra jun. (Ber.1905,58, 1375-1365)

Sodium phenate is prepared as in theKolbe method

C H OH * llaOH = C H OKa * H6 5 6 5 2

When carbon dioxide is passed intothe sodium phenate and heated to 120-130Cunder pressure the resulting product is ortho-BOdoxybenzoic acid (sodium phenoxide-ortho-carboxylic acid)

OKaJQuHOUa.CgH^.COgH --

It is not identical with sodium sali-cylate. It has a greater dissociation tensionthan sodium salicylate. It slov?ly absorbsammonia at ordinary temperatures. It is not


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transformed into sodium salicylate when evapor-ated to dryness \\ith water. It changes complete-ly to sodium salicylate when dissolved in ace-tone. The ortho-sodoxyhenzoic acid, which isthus formed, on heating undergoes an isomericchange into sodium salicylate:

OHCOOlJa

This shows that the C0 enters direct-2ly into the nucleus.

Y/hen sodium salicylate is heated in aclosed tube for 2-12 hours at 248'^, it changesmore or less completely into ortho-sodoxyhenzoicacid.


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CQKGIUSIOU.

The proper v^orking co adit ions forthe process are outlined under "Our Methodof Preparation."

However, for larger yields pressureup to 125 lbs. per so. in, or even highershould ce used.

To use an enameled autoclave witha stirring device would he of decided advan-tage, because it would yield a purer and moreuniform product and it would materially cutdown the time necessary for the completion ofthe reaction.

The yield as well as the quality ofthe product depends mainly on three requisites;the sodium phenate must not ce charred, itmust be dry and well powdered; the carbon diox-ide must bo dry; the temperature must beclosely controlled.


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RE?ESE^TCES

Neues HandwOrterlDuoh der Cheraie - 1890.

Dictionnaire de Ghiinie - 1906.

Thorp, Dictionary of Applied Chemistry, 7.4, - 1913.

Die SyuthetiBchen Darstellimgsmethoden derZohlenstoff-Verbindungen, Dr. Zarl Elbs - 1689.

r/atts, Dictionary of Chemistry, V.5, - 1692.

J. Chern Soc. 114. 11, 137-8.

Ber. S. [Dijmstra, jun. , 1905, 36, 1375-65.


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Preparation of Sal 00 Mark