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Adsorption Experiments with Radium D and Radium E Author(s): John P. McHutchison Source: Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, Vol. 111, No. 757 (May 1, 1926), pp. 134-143 Published by: The Royal Society Stable URL: http://www.jstor.org/stable/94670 . Accessed: 07/05/2014 19:01 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. . The Royal Society is collaborating with JSTOR to digitize, preserve and extend access to Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character. http://www.jstor.org This content downloaded from 169.229.32.136 on Wed, 7 May 2014 19:01:17 PM All use subject to JSTOR Terms and Conditions

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Page 1: Adsorption Experiments with Radium D and Radium E

Adsorption Experiments with Radium D and Radium EAuthor(s): John P. McHutchisonSource: Proceedings of the Royal Society of London. Series A, Containing Papers of aMathematical and Physical Character, Vol. 111, No. 757 (May 1, 1926), pp. 134-143Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/94670 .

Accessed: 07/05/2014 19:01

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

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The Royal Society is collaborating with JSTOR to digitize, preserve and extend access to Proceedings of theRoyal Society of London. Series A, Containing Papers of a Mathematical and Physical Character.

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Page 2: Adsorption Experiments with Radium D and Radium E

134

Adsorption iExperiments with RiRctdum D and Radium E].

By J-OHN P. MCHUTCHISON, M.A., B.Sc., Physical Chemist to the Glasgow and WVest of Scotland Radium Conmmittee, Radiometric Laboratory, the Chemical Department, Glasgow University.

(Communicated by Prof. G. G. Henderson, F.R.S.-Received December 17, 1925.)

Our knowledge of the behaviour of radio-elements in precipitation reactionls is mainly due to Fajans and his co-workers,* who investigated the relation existing between the completeness of the removal of the radio-element from solution and the solubility of its salt. They found that, when a filterable quantity of the precipitate of a common element was brought down in a solution con- taining an infinitesimal quantity of a radio-element, the radio-element itself was precipitated, if its corresponding compound was also insoluble. This general conclusion was later investigated by Fajans and Richter (loc. cit.) with respect to thorium B, and it was further established that the degree of removal of the radio-element was dependent on the solubility of the precipitate of the ordinary element. Thus with very inisoluble precipitates such as bis- muth sulphide and barium sulphate, thorium B was completely precipitated, while less insoluble precipitates like silver chloride carried down only part of the radio-element. It was also suggested that when the precipitate was the insoluble salt of an isotope, the removal of the radio-element was to be ascribed to its solid solution in the isotopic precipitate, whereas removal by precipitates of dissimilar elements was an adsorption effect.

This last fact, the connection between the adsorption of radio-elements by various substances and the solubility of the corresponding active compounds, was the subject of detailed researches by Paneth,f and byHorovitz and Paneth.1 As a result, it was proved that the connection between the magnitude of the completeness of removal of the radio-element and the solubility of the analogous radio-active compound, held for a solid precipitate added to the solution as well as for the case of a precipitate brought down in the solution. Experi- ments have also been conducted in this field by Ebler and van Rhyn? and others.

* 'Ber. deutsch. chem. Ges.,' vol. 46, p. 3486 (1913); ibid., vol. 48, p. 700 (1915). t 'Physikal. Zeitschr.,' vol. 15, p. 924 (1914). :t ' Zeitschr. Physikal. Chem.,' vol. 89, p. 513 (1915). ? ' Ber. deutsch. chem. Ges.,' vol. 54, 13, p. 2896 (1921).

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Page 3: Adsorption Experiments with Radium D and Radium E

Adsorption Expertments with Radium D and Radium E. 135

The general conclusions arrived at may be summarised as follows:-

1. When radio-elements are precipitated along with other precipitates, the solubility product of the active ions present need not be attained before pre- cipitation takes place.

2. A radio-element will be removed by adsorption on a given adsorbent, for which the analogous radio-active compound (that is, the compound of the radio-element containing the same electronegative constituent as the adsorbent) is relatively insoluble ; and the less soluble the precipitate the more completely will the active element be removed.

The object of the experiments to be described was to investigate how far tnese facts are applicable to two radio-elements, when these exist together in solution in radio-active equilibrium: and, in particular, to discover if removal by an isotopic adsorbent was more complete than that by a compound of like solu- bility of a dissimilar element. In the course of the work, results have been obtained which indicate that the half-life period of radium E has a value slightly lower than that usually ascribed to it.

The source of the radium D and radium E was a quantity of radon tubes, which had been used in medical treatment several years ago. From these the later disintegration products of the radium series, radium D, radium E, and radium F, were removed by boiling the tubes in aqua regia, evaporating the solution so obtained to small bulk, adding more nitric acid, evaporating almost to dryness and adding distilled water. When a neutral solution was required the evaporation was continued to dryness, and the active products dissolved in distilled water.

The various precipitates formed in the active solution, or the solids added to the solution, were allowed time in every case to come into adsorptive equilibrium with the radio-elements present. Filtration was performed in a Buchner funnel and the activated precipitates measured on the filter papers; but, before filtering, the supernatant liquid was decanted to prevent any adsorption of the radio- elements by the filter paper,* and the precipitates were washed by decantation. The measurements of activity were made with a beta-ray electroscope through a screen of gold-beater's skin anid two centimetres of air, so as to cut off all the alpha-radiation due to radium F. The experiments are therefore concerned only with radium D and radium E, which are isotopic with lead and bismuth respectively. The activities are expressed in arbitrary units, namely divisions of electroscope scale p3r minute.

* cf. Godlewski, ' Phil. Mag.,' vol. 27, p. 618 (1914).

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Page 4: Adsorption Experiments with Radium D and Radium E

136 J. P. Mcdlutchison.

1. Adsorption by Sulphides. (a) By Precipitation in Acid Solution. Various sulphides were precipitated

by passing sulphuretted hydrogen for 5 minutes through acid solutions (0 * 02 N) of the radio-elements, containing quantities of the several salts so as to give the same mass of sulphide precipitate in each case, which was just sufficieiit to form a very fine film on the filter paper. Several parallel experiments were performed with similar results to those shown.

Table I.

Precipitate. Iniitial activity. Final activity.

Lead sulphide .108 108 Bismuth sulphide .110 110 Mercuric sulphide .109 109 Copper sulphide .93 74 after 35 days Ferrous sulphide (in neutral solution) 93 93

The same quantity of the active solution as used in above series witholut the addition of any other substance was evaporated to dryness on a watch- glass, and gave an activity of 111; and it is therefore apparent that radium D and radium E present together in equilibrium proportions can be completely removed by precipitation along with other substances. Since the mercur; sulphide precipitate was as active as either that of lead sulphide or bismuth. sulphide, it appears that isotopic precipitates have no greater adsorptive power, since certain non-isotopic precipitates can completely carry down the radio- active matter. It will also be noted that the isotopic precipitate exhibits no preferenice in adsorption for its own isotope, as compared with the other radio- element. All the above precipitates contain radium D and radium E in equilibriuim, except copper sulphide, which has precipitated radium E in excess of its equilibrium quantity of radium D, so that the activity declines, till after 35 days or so equilibrium is established between the two radio-elements. The result obtained. with copper sulphide would tlierefore appear to be an abnormal effect, since there seems to be no reason why the copper sulphide should prefer the active isotope of bismuth to the active isotope of lead. Fajans and Beer* found in the course of their experiments that abnormal adsorption did not interfere to any great degree; but the anomalous result obtained above suggests that in the case of the simultaneous precipitation of two radio- elements there may be abnormalities not apparent when dealing with the solution of a single radio-element.

(b) Addition of Sulphides to Active Solution.-Table II shows the results * Loc. cit.

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Page 5: Adsorption Experiments with Radium D and Radium E

Adso7ption Fxperiiments wvith Radium D and Radium E. 137

obtained when sulphides were added to the acid active solution. Sillphides of mercury (-ic), lead, bismuth, and copper were finely powdered and added to the same volume of active solution, which had the same total activity, 111, as in Table I. The mixture was shaken briskly for ten minutes, and the activated sulphides measured on a filter paper as before, parallel experiments being conducted.

Table II.

Precipitate. Initial activity. Final activity. Percentage of Radium 1) Removed.

I 5ead sulphide. 103 83 Abotut 75 per cent. Bismuth suilphide ........................ 61 76 70 Mercuric suilphide ..................... 73 38 35 Copper sulphide. 31 64 60

It is to be noted in these experiments, where two radio-elements are present in equilibrium solution, that there is a very marked difference between the degree of adsorption taking place during precipitation and that occurring on a solid precipitate, since in the first case all the radium ID and its equilibrium quantity of radi-um E could be removed, but in the second not more than 75 per cent. The preference shown by copper sulphide in Table I for one of the radio-elements is here proved to hold for all the sulphides, when these are shaken up withl the active solution, instead of being precipitated in the solution. Lead sulphide and bismuth sulphide, for example, when. formed in the solution, carry down all the radium D and radium E present, but when these sulphides are added to the solution the lead sulphide adsorbs radium. E in greater quantity than its equilibrium quantity of radium D; and bismuth sulphide adsorbs radiumi D in greater quantity than its equilibrium amoulnt of radium E. Mercuric sulphide hias a preferential adsorptive power for radium E and copper sulphide for radium D. The smaller degree of removal in this set of experi- ments is understandable on the basis of the smaller specific surface available for adsorption in the case of a solid added to the solution, as compared with a precipitate actually brought down in the solution. But the selective action displayed as between the two radio-elements present is not readily explained.

2. Adsorption by Chlorides. (a) Precipitation by Hydrochloric Acid. The chlorides of lead, silver, an(d

mercury (-ous) were precipitated with hydrochloric acid by adding it in excess to active solutions containing lead nitrate, silver nitrate, and mercurous nitrate respectively. The very marked differences in the activities of these three precipitates is apparent in the cturves shown in fig. 1, which have been drawn

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Page 6: Adsorption Experiments with Radium D and Radium E

138 J. P. McHutchison.

from the following measurements. The total activity -was 72 in this series of experiments, and also for those detailed in Tables IV and V.

70 AgCt

60-

50 -

2 X / P~~~~~~b C12

t30

t20 -

/ ~~~~~Hg CI

0 2 3 4 5 6 7 8 9 10 10 12 13 14 /5 16 17/ 8 /9 2J lime ini Dzis

Fm. 1..--- Activritie.s of Chloridles precipitated in A4cid1 ,Solution.

.? ~~~~~~~~~~~~~~~~~~~~~

7,-

o / 2 3 OC oZ 6 0i 2 /3 /4 15 6 t7 ifi /9 'Y Time inTDis

FIG. 2.-Activities of Chlorides precipitated in Neutral Solution.

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Page 7: Adsorption Experiments with Radium D and Radium E

Adsorption Experimnents wuith Radium D and Rctdiumn E. 139

Table III.

Timue. 4 Lead chloride Silver chloride Mercurous chloride

T precipitate. precipitate. precipitate.

2 p.m., August 17. 1.8 69 9 0(4 1 p.m., August 19 .18.0 69*5 0*9 12 noon, August 2 1 .245 70*0 1*0 12 noon, August 26 .51.5 70 0 2.0 12 noon, September 5 .60.0 69 4 2 1 5 p.m., September 18 64 8 69 *8 2 2 5 p.m., September 21 65 7 69 8 2 3

.................................... thereafter constant .............. .

It will be observed that the lead chloride precipitate has a small initial activity, which gradually increases due to growth of radium E; and, there- fore, it may be said that lead chloride adsorbs practically only radium D, but this very completely; which might be expected, since the chloride of radium E,likethe chloride of bismuth,is soluble in hydrochloric acid. The silver chloride precipitate removes all the activity, since in hydrochloric acid solution the solubility is very slight. In neutral solution Fajans and Richter* found that silver chloride carried down only some 40 per cent. of thorium B: so that the connection between the degree of removal and the solubility of the precipi- tate holds very clearly in this case. But that this is not the only factor involved is indicated by the fact that the mercurous chloride brings down very little of the active elements at all.

(b) Precipitation by Sodium Chloride Solution. The influence of acidity in the degree of adsorption is shown by a comparison of fig. 1 and fig. 2, which latter shows the curves of activity of the same chlorides, precipitated in neutral solution by sodium chloride solution. Table IV gives the activities.

Table IV.

'rine. Lead ehloride Silver chloride Mercurous chloride T precipitate. precipitate. precipitate.

3 p.m., August 5 .......................6. 640 71i 1 69. 1 2 p.m., Auguist 6 ........................ 56 5 68S5 64-4 3 p.m., August 7 ........................ 50 . 7 65.7 58-7 12 p.m., August 8 ........................ 46)2 58-0 55-5 4 p.m., August 10 ........................ 44-7 50.9 45-3 4 p.m., August 14 ........................ 40*5 48.4 37 1 3 p.m., August 17 ........................ 38 -2 46.5 31*9 12 p.m., August 20 36 * 7 43 .5 30*2 12 p.m., August 26 34.9 42-4 26.1 6 p.m., September 16 32 -1 39 *7 23 -1

.t.................................... thereafter constant .

* Loc. cit.

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Page 8: Adsorption Experiments with Radium D and Radium E

140 J. P. McHutchison.

These readings indicate that the degree of adsorption by different precipitates is greatly affected by the acidity of the solution, as was noted previously bNr Ho.rovitz and Paneth,* with respect to solutions of a single radio-e]lement. In general, radium D is more readily adsorbed in acid solution and radium E in neutral solution w whichl is in keeping with the known facts of the partial -solubility in water of the chloride of radium D, and the solubility of that of ra(iium E in hydrochloric acid solution., since these chlorides are isotopic withl those of lead and bismuth respectively. But there is no obvious explanation of the poor adsorption obtained by the miercurous chloride precipitate in Table III. Accordingly, it has to be remarked that in the case of chloride precipitates as well as of sulphide precipitates, certain abniormalities in adsorption are apparent. The fact that an isotopic chloride has no uinique powers of adsorption is to be decduced from the results shown.

3. Adsorption by Barium iSulphate precipitated in Solution.

The strong adsorptive powers of barium sulphate have been emphasized by Weiser and Sherrick,t and this substance has been previously used. to adsorb radio-elemnents. In the present case, it was desired to test further the main fact emerging from Sections 1 'and 2, namely, that an isotopic precipitate has iio special adsorptive powers as compared with certain non-isotopic precipitates: anid a sulphate precipitate is a most conveniient one to employ, .since lead sulphate, isotopic with the sulphate of radium D, is also insolubl.e in neutral or dilute acid solution. To equal volumes of the same neutral solution -of radium D and radium E, solutionis were added as shown, and the activities of the resulting precipitates determined.

Table V.

To ineutral solutioIi of radium 1) annd Ilitiall activity. Fiial atctivitv radiumn E added. (after 35 da,ys).

, _ . _ _ _ _ _ ~ ~~_, _ _ , __ _ _ ,., ,

1. Barium nitlatet a.nd sodiumi sulphate . .... . 6 f 65 2. Barium nitratc andi(L execss sulphric a( id ........ 1 5 65 5 3. 'Bariunm nitnate and sodium suliphate in faintly1

alkaline sol1uu ofl .......................................... 72 72 4. 'Barium tnitrate, lead nitrate, ancd sodium

sulphntct ..............6 sulpll~~~~~~~~.31e.. .. ... .... .............. . .... .... ..... i}( 5. Lead mitrate and sodiumiii sulphate . 74) 70 (6. Lead riitiate and excess sulphuric acid . . 22 69

* Loc. cit.

f 'Joiirni. Phvs. Chem.,' vol. 23, p. 205 (1919).

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Page 9: Adsorption Experiments with Radium D and Radium E

Adsorption Experiments wttith Radtium D and Radium E. 141

These results show very clearly that the activity of the isotopic precipitate (lead sulphate) is no greater than that of the non-isotopic precipitate (barium sulphate). The influence of sulphuric acid in increasing the total adsorption (as noted by llorovitz and Paneth) is not apparent. But it will be noted that, when barium sulphate is precipitated by sulphuric acid in excess, radium D and radium E are completely adsorbed, although the sulphate of radium E, like bismuth sulphate, is soluble in sulphuric acid solution; if, however, lead sulphate is precipitated by sulphuric acid in excess, radium D is removed in excess of its equilibrium quantity of radium E. A precisely similar fact is observable in the chloride precipitations ; and only in this case does the iso- topic precipitate appear to possess any preferential powers.

4. Other Adsorptions.

(a) By Calcium Carbonate.-Calcium carbonate was precipitated with calcium chloride and sodium. carbonate in a quantity of the active solution; and also along with basic lead carbonate in a simnilar quantity of solution. In both cases radium D and radium E were completely removed, the presence of the- carbonate of lead, i.sotopic with radium D, not affecting either the degree of adsorption or the ratio of D to E removed in any way.

(b) By Ferric Hydroxide.-Ferric hydroxide precipitated in an active solution brought down all the active matter. It has been noted* that ferric hydroxide adsorbs radium B and radium C, and also thorium B and thorium C in different proportions depending on the degree of acidity of the original solutions: and the effect is ascribed to the passing of the radioactive matter from the ionic to the colloidal state, the change being governed by the acidity of the solution. In the case of solutions of radium D and radium E varying in acidity from 0 0005 N to 0 01 N, no variation in the ratio of radium D to radium E was found, both elements being comipletely removed. On the basis of the colloidal theory advanced by Cranston, one may conclude that in such acid soluitions radium 1) and raditum E are present completely in the ionic con- dition, which agrees with the crystalloidal condition as previously determined for them by Paneth on the basis of dialysis experiments.t

* Cranston and Burnett, ' Journ. Chem. Soc.,' vol. 119, p. 2036 (1921); and Cranston and Huitton, ibid., vol. 121, p. 2843 (1922); and ibid., vol. 123, p. 1318 (1923).

f 'Kolloid-Zeitschr.,' vol. 12, p. 1 (1913).

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Page 10: Adsorption Experiments with Radium D and Radium E

142 J. P. McHutchison.

5. Deternination of the Half-life Period of Radium E by adsorption on Blood Charcoal.

Specially purified blood charcoal thoroughly shaken up with the active solution adsorbed all the radium E, but only about 70 per cent. of radium D. The ratio of radium D adsorbed to radium E adsorbed seems to bear no relation to the relative quantities of these radio-elements present in the solution. In this case there is no similarity between the adsorbed matter and the adsorbent, and the radio-elements are present in the form of soluble nitrates ; so that the effect is a true adsorption one, without the complication of any precipitation pheno- mena. This apparently selective adsorptive action of blood charcoal is being investigated with respect to solutions of radium D and radium E in various solvents.

If to the active solution a quantity of lead as nitrate be first added, and the adsorption on blood charcoal determnined, practically only radium E will be adsorbed, since the infinitesimal quantity of radium D in the solution will have to compete for adsorption with the comparatively very large quantity of its isotope, lead. This experiment was repeated several times, from 1 to 10 grams of lead nitrate being added in different tests, and the activity on the filter paper was found to decay in every case practically to zero, which indicates that radium E alone was present to the degree of accuracy of measurement claimed, viz., 1 per cent. In this way a redetermination has been made of the half- life period of radium E, in view of the fact that Bastings' value, 4 98 days,* suggested that the original value of 5 days, as determined by Antonofft and others, was more accurate than the lower value of 4 85 days, as advanced later by Thaller.j Details are given in Table VI of two of the four determina- tions made, all of which gave 4 9 days as the period, to an accuracy of 1 in 200. Column A in each case shows the activity obtained by measurement, while column B gives the theoretical numbers obtained by calculation on the basis of a half-life period of 4 9 days.

The experimental values and the theoretical numbers calculated on a basis of 4 9 days as the half-life period are in good agreement. The result confirms Thaller's value, further confirmation of which has been obtained recently by Fournier, who gives the value 4 86 days in a paper? published several months after the above experiments were performed.

* ' Phil. Mag.,' vol. 48, p. 1075 (1924). t 'Phil. Mag.,' vol. 19, p. 825 (1910). 1 'Wien. Ber.,' vol. 121, p. 1611 (1912). ? 'Comnpt. Rend.,' vol. 181, p. 502 (1925).

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Page 11: Adsorption Experiments with Radium D and Radium E

Adsorption Experimnents with Radium D and RadiUm E. 143

Table VI.

I. II.

Activity in Arbitrary Units. Activity in Arbitrary Units.

'Time in Time in dilne

in B. Theoretical days. B. Theoretical days. A. Experi- for Radium E ys. A. Experi- for Radium E

mental. with period mental. with period 4 9 days. 4 9 days.

0.0 77.3 77.3 0.0 49 0 49 0 2-0 600 58-3 1.0 42.8 42-6 2-96 53-4 50.9 2 0 36 6 36-9 4.04 43-6 43.7 3.04 32-3 31-9 4.875 38 9 38-8 3 96 29.2 28 0 7.04 28-6 28 6 5 08 23-8 23*9 9 04 23-1 21*7 6*125 20;5 20.6

20-0 5*5 4-6 13-04 8.5 7.7 25-79 3-6 2 0 22-96 2.1 1.9 69-0 0 2 lnil 73*0 nil nil

Synopsis. The results enumerated in this paper may be summarised as follows: (1) Previously known facts regarding the adsorption of a single radio-

element from its solution, either by a precipitate formed in the solution or by an added solid, are in general found to hold for the simultaneous adsorption of the two radio-elements, radium D and radium E, when present in radio- active equilibrium. But it is pointed out that the results in several cases are influenced by abnormal adsorption effects.

(2) Isotopic precipitates possess no greater adsorptive powers than certain non-isotopic precipitates, which can completely carry down the radio-elements.

(3) But an isotopic precipitate, formed under such conditions that one of the two analogous radio-active compounds is soluble, exhibits a preference for its own isotope, whereas a non-isotopic precipitate displays no such preference.

(4) The addition of a soluble lead salt to a solution of radium D and radium E stops the adsorption of radium D by charcoal, and in this way radium E has been extracted in a state of great purity.

(5) The half-life period of radium E has been so determined as 4 - 9 days.

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