V 
 
 J 
 
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 I 
 
 
 
 X 
 
THE EXTRACTION AND PURIFICATION 
 OF CAESIUM SALTS 
 
 BY 
 
 JOHN DRISCOLL CONATY 
 
 THESIS 
 
 FOR THE 
 
 DEGREE OF BACHELOR OF SCIENCE 
 
 IN 
 
 CHEMISTRY 
 
 COLLEGE OF LIBERAL ARTS AND SCIENCES 
 
 UNIVERSITY OF ILLINOIS 
 
 1922 
 

 to 
 
 UNIVERSITY OF ILLINOIS 
 
 i92_2__ 
 
 THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION BY 
 
 JQHK_DftI_SC_OLL_C^^^ 
 
 ENTITLED__THS_MTMQTI_Qli_ANp__PURl£XCMIM__QF_Cj^_SIU^^ 
 
 IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS FOR THE 
 DEGREE OF Bac_he_lo_r p_f__Scjience__i^^^^^ 
 
 
 Instructor in Charge 
 
 Approved : 
 
 /I Ct / q HEAD OF DEPARTMENT OF C_HEMI_ST_RY_ 
 
 i 
 
Digitized by the Internet Archive 
 
 in 2016 
 
 
 https://archive.org/details/extractionpurifiOOcona 
 
Acknowledgement . 
 
 The author wishes to ta,ke this opportunity to 
 express his sincere thanks to Professor B.S. Hopkins 
 at whose suggestion this work was carried out and to 
 whose aid and advice its successful completion is 
 largely due. 
 

Tabla of Contents. 
 
 I. Historical 
 
 II. 3xtraction of Caesium from Hollucita 
 
 A. Decomposition of the Llaterial 
 
 B. Precipitation of Caesium as the 
 
 Double Lead Salt According to the 
 Method of ¥ells. Page 2. 
 
 e. Precix-)i tation of Caesim as the 
 Double Antimony Salt According to 
 the Method of Godeffroy Page 3. 
 
 D. Discussion of the Results and 
 
 Precautions Page 3. 
 
 Page 1. 
 
 Page 2. 
 
 E. Diagram of Method for the 
 
 Extraction of Caesiura from 
 Pollucite as Cs^Sb^Clg Page 5. 
 
 III. PractionG.1 Crystallization of the 
 Alums of the Alkali Metals 
 
 A. Historical Page 6. 
 
 B. Plan for Systematic Practional 
 Crystallization of the Alkali 
 
 Metals Page 7. 
 
 C. Results Obtained fro.m Praction- 
 
 ation Page 8. 
 
 D. Solubility of cs and Rb in the 
 
 Presence of yunmoniua Alum Page 9. 
 
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IV. Surmnary 
 
 Page 10 
 
 References 
 
 Page 11 
 
 V 
 
Th9 "Extraction and Purification 
 of Caesium Salts. 
 
 Hi storical 
 
 In 1860 Bunsen and G. Hirchluof f wnils investigating tne 
 mineral waters of Burkheim evaporo.ted dovm forty tons of 
 v/ater and removed tlie alkaHi eartiis and lithia witn ammonium 
 carbonate. The filtrate snov/ed tjie spectral lines tor sodi’um, 
 potassium and litnium, “and, "besides tnese, tv/o splendid lines 
 near the blue strontum line Bunsen and Kirchiiolf add: 
 
 “As no elementar 3 ,' oody produces two blue lines in tni s 
 portion of the spectru.'a we may consider tne existence of tni s 
 Hitherto unknown alkaline element was placed beyond doubt. 
 
 The tacility witii whicn a few tnousandtns of a miliigrtim of 
 tni s bod;^’" may be recognized by tne brigiit blue of its in- 
 candescent vapor even wnen mixed witn large quantities of 
 more common alkalies, has induced us to propose for tne name 
 caesium (and tiie ^'mbol (js) derived from tne Latin caeslus, 
 used to designate tne blue of tne clear sky". 
 
 Caesium is found widely distributed in nature in small 
 amounts Lepidolite (Li ,E,Na,F,Al(Si 03 ) j) a mineral occurring 
 in considerable quantities near Pala, San Diego Co., Calif., 
 also at Paris and nebron, :ie . , contains from .3-1% Cs^O. 
 Pollucite a mineral occurring on tne island of Elda and at 
 Hebron, Me,, contains from 30-35% CS 2 O . 
 
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2 . 
 
 ^traction of Caesium from Pollucita 
 Decomposition of tlie Material 
 Tile mineral was finely pulverized by grinding in a Ijall 
 mill, placed in large evaporating disn.es and digested from 
 48 to 60 hours v/itn dilute nydrocnioric acid (sp.gr. I.l2). 
 
 At the end of this period tne mixture was evaporated to di%*- 
 ness on tne water datn alter wnicn it was carefully heated 
 over a free flame to dehydrate tne silicic acid. The material 
 was then taken up with v/ater and enough dilute hydrochloric 
 acid added to dissolve the iron salts, and the silica filtered 
 off . 
 
 Precipitation of Caesiun as the 
 Double Lead 8alt According to the Method 
 of Wells 
 
 Several methods are described in the literature for the 
 isolation of caesium from the nydrocnioric acid extract. Wells'^ 
 has recommended the use of tne yellov/ salt 2CsCl PbCl^ in 
 which tne precipitation is made by adding a hot concentrated 
 solution of tne calculated amount of lead nitrate to the crude 
 hydrochloric acid extract. Chlorine gas is then passed in 
 until the solution is saturated. After allowing to stand for 
 ten to twelve hours tne solution is decanted from the pre- 
 cipitate of 2GsCl PbCl^. Tne precipitate is then boiled with 
 ammonium carbonate after which the Pb O 2 filtered off. 
 
 only one run was made on a samx^ls of Maine pollucite as 
 tne yield of caesiuia chloride v/as veiy small as compared with 
 the heavy and large amount of precixJitate forraed and the 
 
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dil’ficulty in v;orking v/itJri free chlorine. 
 
 
 Precipitation of caesium as the 
 Double Antimony Salt According to the 
 
 Method, of Godeffroy. | 
 
 i 
 
 A veiy le.rge series of salts are known of the general | 
 
 type R M X where R is potassium, caesium or ammoniiirij , I' a | 
 
 {• 
 
 f 
 
 heav;^^ metal antimony, arsenic, mercury' or copper, and A a | 
 
 halogen. ! 
 
 Many years ago Godefiroy^ recoiamended tiie extraction of 
 caesium as the double salt of antimony prepared by trea.ting 
 the hydrochloric acid extract with a strong hot solution of 
 antimony trichloride tne pale yellow salt 3CsCl 2SbCl-z having 
 definite crystalline form, sepa.rating out on cooling. This 
 salt v/as filtered on Buchner funnel, a.nd v, 'ashed vifch dilute 
 hydrochloric acid after which it was suspended in v/ater and 
 at first was decomposed with hydrogen sulfide, but a.s**this 
 consumed too long a time it v;as in subsequent runs decomposed 
 by boiling with dilute ammonium hydroxide, the antimonous 
 oxide being filtered off. The solution of mixed chlorides 
 was then evapora.ted to a small volume, nitric acid added and 
 the evaporation taken to dryness^. The fused. nitre.te v/as then 
 recry' stall i zed. from hot v/ater from v/hich it crystallized out in 
 large prisms like potassium nitrate. 
 
 Discussion of the Results and Precautions. 
 
 The maximum yield of crystallized, caesium nitrate that was 
 obtained by this method was 7%, but this low yield we,s due to 
 a poor grade of pollucite as the solutions that were decanted 
 from tne caesium antimony chloride precipitate were 
 
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 found to have only traces of caesium remaining in them, since 
 it was found impossible to obtain arry of the double lead salt 
 irom this solution, the latter being tne more insoluble of the 
 two salts. 
 
 In tne precipi te.tion of the 3Cs Cl 2SbCl„ salt Groups I, ll, 
 
 o 
 
 III and Iv metals do not interfere as the racid concentration 
 is sufficient to maintain their solution. If the iron were removed 
 as the hydroxide, large quantities of caesium v/ould be lost 
 due to occlusion unless the ferric hydroxide be reprecipitated 
 several times. 
 

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5 
 
 Diagram of K<9thod for the 
 ijjxtraction of Caesian from Pollucite 
 as GSjSb^Clg 
 
 SiO^ ^tc. 
 
 Pollucit e 
 
 Boil HCl sp.gr. 1.12 48-60 hours 
 
 Uvaporatiou and Filtration 
 
 Solution; Alkali ..petals, 
 
 CsCl PbO. 
 
 Recr>" stall! zed 
 
 from hot water 
 
6 
 
 Fractional stall izat ion of the 
 Alums of the Alhali Metals. 
 
 The soluhilities of the alums of sodium, ammoniura, 
 potassium, caesium and rubidium as stated in Comey are as 
 f ollov/s: 
 
 
 Parts in 100 Parts V/ater 
 
 T «mp . 
 
 Pota.ssi'om alum 
 
 13.5 
 
 17® 
 
 Ammonium alum 
 
 8.74 
 
 17.5 
 
 SodiuTi alun 
 
 103.1 
 
 10 ® 
 
 Rubidium alum 
 
 2.27 
 
 I 7 P 
 
 Caesium alum 
 
 0.619 
 
 17® 
 
 Rohinson and Hutchins^ v/ere the first to point out 
 this difference in solubility and recommended it as a me.ans 
 of separating caesium and rubidium from lithiun and potassium 
 in lepidolite after the mineral had been decomposed v\ritn 
 hydrofluoric acid. They also pointed out the difference in 
 solubility of caesium and ruoidiuin alums and recommended a 
 fractional crystallization for the separation of these elements. 
 Hov;ever, tne difference in solubility of ca.esiua and rubidium 
 aluas is not great enough to allovr a rapid separation of 
 these elements, v/hile the difierence in solubility of the alums 
 of the rare metals and those of the common ones is suificient 
 
 to make a sati sfactoiy method of separation. 
 
7 . 
 
 Plan for Systematic Practional cry atallizc tion 
 of Alums 01 tne Alkali Metals. 
 
 i 
 
 M 
 
 The pollucite was decomposed in tne usual manner with | 
 ny drocnloric acid and after evaporation and filtro,tion of | 
 
 tne silica the hydrochloric acid extract was concentre ted i 
 
 witn sulfuric acid. On cooling the mixed aluius ciystaliized | 
 
 r 
 
 out. 'i'nis is the most advantageous and rapid method to ( 
 
 remove caesiuiri from pollucite. The mixed alums vdiile con- ! 
 
 f 
 
 taining traces of iron were in two to three ciy stallizations t 
 free from iron. 
 
s. 
 
 Tile alujTis (1) from 3400 grams of pollucite containing 
 approximately 12/^ CS 2 O were subjected to ^'Stematic fra.ctional 
 cry stall iza,ti on by dissolving in not water and stirring 
 vigorously wnile tii9 solution yjaz cooling to destroy the 
 supersaturated solutions which these alums especially caesium 
 tend to form. The motner liquor v/as concentrated until on 
 cooling it yielded a second crop of ci^’stjils, (6) and the 
 ne \7 mother liquor concentrated again to yield a third crop 
 of cr;>’stals (12) and so on. The crystals in the first 
 crystallizing disn (2) were d.issolved in not water and allow- 
 ed to crystallize again (4) the supernatant liquid (5) being 
 used to dissolve the^ second crop of cr;>'stals (6) and 
 allowed to re cr;>' stall ize tni s scheme being continued in all 
 the dishes. The cr;>*stals separa.ting in the first dish wrere 
 repeatedly recrystallized from hot v/ater. By tnis system 
 tne cry^stals in tne first of the series were tJie more 
 insoluble alur^s of caesium (and rubidium) while those in 
 tne lov\rer end of tne series were tne more soluble alums 
 namely sodium and potassium. 
 
 Results Obtained from Rractionation 
 of the Alums. 
 
 After the alums from the pollucite were recrystallized 
 nine times the crystals in the insoluble end of tne series 
 gave strong tests for caesium and traces of sodium, and 
 potassium while the crystals in the more soluble end (ninth 
 dish) gave strong tests for sodium and potassium a.nd traces 
 of caesium. 
 

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 crystallizations the spectruLu saioived no evidence of tne 
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 dish showed nearly pure caesium with traces of sodium. 
 
 Solubility of Caesium and Rubidium in the Presence 
 
 of Ammonium Alum. 
 
 7 
 
 browning and Spencer have determined the solubility 
 of caesium ana rubidiuiL in a saturated solution of ammonium 
 aluiii. They found that Ic.c. of a solution of RbCl containing 
 0.0002gm. v.'ould give a perceptible precipitate v/hen treated 
 with 5c. c. of a saturated solution of ammonium alum and that 
 Ic.c. of a csCl solution containing .00005gm. cs v/ould give 
 a precipitate of caesiun} a.lum. 
 
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 A study of the various methods for the decomposition 
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 that the most convenient method for the isoia.tion of caesium 
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 acid. It has the advantage over precipitations of douuie 
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