PERMANGANATE AS A REAGENT FOR THE SEPARATION AND
DETERMINATION OF CESIUM
DISSERTATION
Presented in Partial Fulfillment of the Requirements for the Degree Dootor of Philosophy in the Graduate School of The Ohio State U n iv e r sity
By
WALLACE HENRY DEEBEL, A .B ., Ed.M ., M.So.
******
The Ohio State University
1957
Approved bys
A dviser Q Department of Chemistry ACKNOWLEDGMENT
The author hereby expresses his sincere appreciation to Dr. Earle R.
Caley for his suggesting this investigation anc, for his advioe and guidance during its course.
i i TABLE OF CONTENTS
Page
Introduction ...... I
M a te r ia ls ...... 5
Experiments on Precipitation of Cesium Permanganate...... 11
Repreoipitation of Cesium Permanganate ...... 20
Behavior of Ammonium Permanganate Reagent toward
Rubidium Chloride Solutions ...... 22
Behavior of Ammonium Permanganate Reagent toward
Potassium Chloride Solutions ...... 25
Experiments on Precipitation of Cesium Permanganate in the
Presence of Rubidium...... 2?
Experiments on Precipitation of Cesium Permanganate in the
Presence of Potassium...... SO
Determination of Cesium by a Volumetric Method ...... 53
Stability of Ammonium Permanganate Reagent ...... 34
General Discussion ...... 3 7
Recommended P roced ure...... 38
Notes on Procedure...... 4 0
Summary...... 41
Bibliography ...... 4 3
i i i LIST OF TABLES
T able Page
1. Solubility of the Permanganates of Potassium, Rubidium, and Cesium at Certain Temperatures .... 4
2. Molar Concentration of the Alkali Metal Ions in a Permanganate Solution at Certain Temperatures. . . . 4
3. Attempted Recovery of Cesium from Concentrated Solutions of Cesium Chloride ...... 12
4. Attempted Recovery of Cesium from a Solution of Cesium Chloride in Propionic A cid...... 13
5. Recovery of Cesium from Solutions of Cesium Chloride Evaporated to 1 Drop, Diluted with Various Volumes of Propionic Acid, and Precipitated with One-and- a -H a lf Times th e T h e o r e tic a l Amount o f Ammonium Permanganate ...... 15
6 . Recovery of Cesium from a Solution of Cesium Chloride Evaporated to 1 Drop and Treated with an Excess of Ammonium Permanganate ...... 15
7. Recovery of Cesium Precipitated under Standard Conditions 17
8 . Recovery of Cesium from a Solution of Cesium Chloride Containing 5.0 mg. Cesium per ml. under Standard C o n d it io n s...... 18
9. Recovery of Cesium from a Solution of Cesium Chloride Containing 2.0 mg. Cesium per ml. under Standard Conditions ...... 19
10. Reoovery of Cesium with Various Concentrations of Reagent under Standard Conditions...... 20
11. Preliminary Experiments on Behavior of Ammonium Permanganate Reagent toward Rubidium ...... 23
12. Behavior of Reagents of Lower Concentration toward R u b id iu m ...... 23
13. Preliminary Experiments on Behavior of Reagent toward Lower Concentrations of Rubidium ...... 24
i v LIST OF TABLES (CON«T)
Table Page
14. Behavior of Reagents of Lower Concentration toward Lower Concentrations of Rubidium...... 25
15. behavior of Ammonium Permanganate Reagent toward P otassium ...... 26
16. Behavior of Reagent toward Lower Concentrations of Potassium...... 27
17. Apparent Recovery of Cesium from a Standard Solution of Cesium Chloride Containing Rubidium Chloride. . . 28
18. Apparent Recovery of Cesium from a Standard Solution of Cesium Chloride Containing Smaller Amounts of Rubidium Chloride ...... 29
19. Apparent Recovery of Cesium from a Standard Solution of Cesium Chloride Containing Smaller Amounts of Rubidium Chloride...... SO
20. Recovery of Cesium from a Standard Solution of Cesium Chloride Containing Potassium...... 31
21. Recovery of Cesium from a Standard Solution of Cesium Chloride Containing Smaller Amounts of Potassium . . 32
22. Recovery of Cesium from a Concentrated Solution of Cesium Chloride Containing Other Alkali Chloride . . 33
23. Volumetric Estimation of Cesium ...... 34
24. Stability of Ammonium Permanganate Solutions...... 35
25. Maximum Volumes and M olarities of Ammonium Permanganate Reagent Allowed without Precipitating One Alkali Alone in a Chloride Solution ...... 38
v PERMANGANATE AS A REAGENT FOR THE SEPARATION AND
DETERMINATION OK CESIUM
INTRODUCTION
Because of the sim ilarities in the chemical behavior of their ions
and in the solubilities of their salts, the separation of cesium from
rubidium and potassium, or the determination of cesium in the presence
of rubidium and potassium, has been found to be one of the most d iffi
cult problems of inorganic chemical analysis.
In the perchlorate, oobaltinitrite, and chloroplatinate methods
for potassium, cesium is precipitated without any separation ( 7 ).
Noyes and Bray ( 6 ) have given details for using the perchlorate method
of group separation, for conversion of the alkali chlorides to oobalti-
n itrites, and for separation of cesium and rubidium from potassium
as the triple nitrites. They specify three reagents for the separation
of cesium from rubidium and for its determination. First, antimony tri
chloride is used to precipitate most of the cesium, then sodium hydro
tartrate or sodium 6-chloro-5-nitrotoluenemetasulfonate to precipitate
most of the rubidium, and finally silicotung3tic acid for the precipi
t a t io n o f th e r e la t iv e l y sm all amount o f rem aining cesiu m . The method
is time-consuming.
O'Leary and Papish (7) have described the separation and determin ation of the three elements by also using three reagents in succession.
Precipitation with 9-phosphomolybdic acid separates rubidium and cesium from potassium. Silicotungstic acid separates cesium from rubidium. Chloroplatinic acid precipitates cesium. Although the method may be an
improvement of the preceding method, the separations are not entirely
clean-cut (3).
After finding that existing methods did not give satisfactory re
sults when applied to rocks and minerals, Wells and Stevens (10) developed
a method for the determination of cesium and the other alkalies. They
noted that large quantities of rare alkalies had been used by previous
investigators in their analytical studies, whereas these elements usually
occur in small quantities in actual samples. The chloroplatinates of
potassium, rubidium, and cesium, adiich are separated from the other
alkalies as a group, are weighed, and converted to chlorides. After
removal of the platinum by precipitation with hot dilute formic acid,
rubidium and cesium are separated from potassium by treatment of the solu
tion of chlorides with gaseous hydrogen chloride and absolute aloohol
saturated with the gas. The extract of rubidium and cesium chlorides
then contains only 0.6 mg. of potassium chloride. Rubidium is preoipitated
as the sulfate from this extract by the addition of alcoholic ammonium
sulfate. This method is also time-consuming.
Hillyer (4), in using the method of Wells and Stevens, has shown that as many as six extractions m y be necessary, if the sample oontains much rubidium or cesium, as for example in his analyses of samples of pollucite (9) that contained over 30 per cent of cesium oxide. To reduce the number of extractions, he suggests three procedurest 1 ) to use an aliquot part, if there is enough potassium to furnish 0 . 6 mg. of potassium chloride for each extraction, 2 ) if potassium is low, to substitute for the absolute aloohol a mixture of concentrated hydrochlorio aoid and aloohol, which dissolves 3.1 mg. of potassium chloride and about ten
times as much rubidium chloride and cesium chloride as the absolute
alcohol, or 3) if potassium is very low, to omit the extraction of
cesium chloride from the mixea chlorides and to treat the chlorides as
cesium chloride containing a trace of potassium chloride. After
using any of the three procedures, rubidium is separated with alcoholic
ammonium sulfate, as direoted by Wells and Stevens (10). H illyer’s
modification avoids an exoessive number of extractions, but the method
is still time-consuming.
Wells and Stevens (11) in also discussing the analysis of a pollu-
eite containing a high percentage of cesium oxide suggested the separa
tion of the bulk of the ohloroplatinate of cesium from that of potassium
and of rubidium by several fractional crystallizations, followed by
t h e ir ( 1 0 ) procedure for separating cesium from potassium and rubidium
in the soluble ohloroplatinate solution with alcoholic ammonium sulfate.
Although this modification may shorten the method considerably, it is
still not rapid.
This present investigation was undertaken with view to developing
a more rapid method for the separation of cesium from potassium and
rubidium and for its determination in their presence. A survey of tho
solubilities of cesium compounds suggested that the solubility of cesium permanganate was low enough for quantitative precipitation of the element, especially at low temperatures. Patterson ( 8 ) gives the solubility of cesium permanganate in a saturated aqueous solution at 1°C. and at 19°C.
He also gives the solubility of rubidium permanganate at 2°C. and at 19°C., and of potassium permanganate at 0°C. These data, together -with the solubility of potassium permanganate at 19.8°C. as given by Baxter,
B oylston , and Hubbard ( 1 ) , are shown in Table 1.
TABLE 1
SOLUBILITY OF THE PERMANGANATES OF POTASSIUM, RUBIDIUM, AND CESIUM AT CERTAIN TEMPERATURES
°c. KMn04 RbMn04 CsMn04 Grams Grams Grams
0 2 .8 4 #• • • 1 • ••• • • • • 0 .0 9 7 2 • • * • 0 .4 6 • • • » 19 • • • • 1.06 0 .2 3 19.8 5.96* • • • • • • « •
* This figure is for g. per 100 g. of solution. The other figures are for g. per 1 0 0 cc. of solution*
At 1 O C. the solubility product for cesium permanganate is 1*5 x 10 and the molar concentration of the cesium ion in solution is 3.9 x 10“3.
The data of Table 1 in terms of the molar concentration of the alkali metal ions are shown in Table 2.
TABLE 2
MOLAR CONCENTRATION OF THE ALKALI METAL IONS IN A PERMANGANATE SOLUTION AT CERTAIN TEMPERATURES
Concentration in Moles per Liter
°C. K+ Rb* Cs+
0 1.80 x IQ- 1 • • • • « ••• 1 » • • # .... 3.85 x 10~ 5 2 • « «• 2 .2 5 x 10" 2 . . . . 19 • • • • _ 5 .1 8 x 1 0 - 2 9.15 x io-3 19.8 3 .7 7 x lO" 1 • • • • • • • • For the solubilities at the three lowest temperatures, the ratios to
cesium are: K : Cb * 47 * lj Rb * Cs * 5.8 : 1, and the ratios
at the higher temperatures are;
K i Cb 8 41 i lj Rb j Cs = 5.2 : 1.
Although the solubility of cesium permanganate at 1°C. is only 0.97 mg.
per ml. (Table 1), the possibility appeared that it might still be lower o at 0 C. The above ratios, though approximate, indioated that potassium
or rubidium permanganate might be held in solution while precipitating
cesium permanganate.
MATERIALS
CESIUM CHLORIDE. Cesium chloride from a commercial source was
examined speotrographically and found to contain these eight impurities:
Na, K, Rb, Mg, Ca, Al, Cr, and Fe. Four bottles^ containing cesium
diohloroiodide were likewise examined with the following results:
B o ttle No. Im p u rities Found
12 Na, Mg, Al, Tl, Si, Sb, Cr, Fe, Cu, Ag
13 Na, Mg, Ca, Al, Tl, Sb, Cr, Fe, Cu
14 Na, Rb, Mg, Ca, Sr, Al, Tl, Sn, Cr, Mn, Fe, Hi, Cu
15 Na, Rb, Mg, Ca, Al, Tl, Si, Sn, Cr, Mn, Fe, Cu
The copper present as an impurity was probably derived from the cutters used to sharpen the electrodes. Although none of the preparations had fewer impurities than the commercial cesium chloride, that of bottle 13 was selected for purification because of the absence of potassium.
T------These were student preparations. They were contributed by Dr. K. V. Moyer, Department of Chemistry, The Ohio State University. 6
The selected lot was weighed and then heated at 200°C. for 54 hours
in order to volatilize the iodine monochloride. To confirm the almost
complete removal of iodine monochloride, the weight of the residual
cesium chloride was compared wi-fa the calculated weight of cesium chloride
based on the weight of the oesius. dichloroiodide taken. The difference
was 0.0185 g. or 0.07/4. The color of the reagent had changed from yellow
to white with a feint yellow color under the surface. Foreign particles
of two kinds, black and reddish, were present, which were removed mechani-
oally with a pair of tweezers. Two more heatings at 200°C. followed by
weighings showed losses in weight of 1.9 mg. and 1.6 mg. respectively.
Conversion to the chloride was then considered to be complete.
This cesium chloride was further treated to eliminate other impurities.
It was dissolved and filtered to remove a small amount of insoluble matter,
whioh appeared to be silica and pieces of glass. This and all subsequent
filtrations for purification were made through close-grained quantitative
filter paper. On evaporating the pale yellow filtrate to dryness, the
residue was mostly white, but partly yellow. This residue was dissolved
in water, the solution was heated, hydrochloric aoid was added, and the
solution was filtered. Ammonium hydroxide was added to the filtered solution, which was again filtered. On evaporating this filtrate to dryness the residue was still not completely white.
Acetone, in which cesium chloride is relatively insoluble, was used t o make a number o f r e p r e c ip it a t io n s . The p o rtio n s o f p r e c ip it a te were collected and dried in a platinum dish at 250cC. and then heated to about
490°C. (2). The salt was pulverized in a porcelain mortar and heated to 515°C. After dissolving the salt, filtering the solution, evaporating tho filtrate to dryness, and repeating this series of operations a number
of times, the dried salt was again heated, this time to 590°C., in a
platinum dish, and cos led. The salt was now white with some yellow
underneath. It was heated to 670°C., where fusion occurred (2). The
melt was cooled, and upon dissolving the mass, the yellow color of the
solution showed that the preceding treatments had left the cesium
chloride still contaminated.
Consequently, the solution was treated with hydrogen sulfide first
in acid medium, then, in basic medium, and the precipitated impurities
were removed by filtration. After another treatment with hydrogen sulfide
in basic medium, the evaporated filtrate gave a nearly white salt. To
remove calcium the solution of the salt was treated twice with ammonium
oxalate, according to the procedure of Kolthoff and Sandell (5).
Magnesium was removed with 8 -hydroxyquinoline by using the procedure of
the same authors (5). After several treatments with 8 -hydroxyquinoline,
the solution was boiled on an electric hot plate for an hour to remove
the organic ions. After the solution was evaporated to dryness on the
steam plate, the salt was generally white. It was heated to 595°C.,
and cooled. After discarding a minor portion, yellow in color, the white
cesium chloride was pulverized, bottled, and weighed. To confirm the purity of the cesium chloride, qualitative spectrographic analyses were made, which showed that the following four impurities were s till present*
Na, Mg, Ca, and Si. Silicon was present as a trace and the other three were very likely in insignificant and non-interfering amounts. A standard solution of cesium chloride, containing1 0 . 0 mg. o f cesium per m l. was finally made. RUBIDIUM CHLORIDE. Rubidium chloride, of two lot numbers, from the
Bame commercial source as the cesium chloride, was examined spectro-
graphically. One lot number contained six, and the other eight, impuri
t ie s *
Lot im p u r itie s Found
a Na, K, Mg, Ca, Si, Cr
b Na, K, Mg, Ca, A l, T l, Cr, Ag
The reagent of Lot a, having the fewer impurities, was selected for
purification. It was purified in essentially the same way as the cesium
chloride, except for some omissions, which shortened the process. The
omissions were* 1 ) precipitations in acetone were not made, 2 ) few er filtrations of observed foreign matter were needed, 3) a platinum dish was not resorted to, and 4) the highest temperature of the muffle for final heating to complete whiteness was 500°C. (2). More precipitations of calcium and magnesium were, however, made for the rubidium chloride
(three and seven respectively) than for the cesium chloride (two and four respectively). The purified rubidium chloride was weighed and bottled for use. Its purity was confirmed spectrographically. The spectrographic analysis showed that the same final impurities were still present as in the cesium chloride and in the same trace or non-interfering amounts* It did not show that potassium was present, even though no attempt had been made t o remove th a t im p u rity .
POTASSIUM CEI AMMONIUM PERMANGANATE SOLUTION. To p r e c ip ita te cesium as th e per manganate, a reagent of ammonium permanganate was selected, in preference 9 to an alkali permanganate, so as to avoid the introduction of extraneous alkalies. Barium permanganate, "C.P.”, and ammonium sulfate, ”Reagent- Grade", were used to produce the reagent by the following reaction* (NH4 ) 2 S0 4 + Ba(Mn0 4 ) 2 — > 2 NH4 Mn0 4 + 3aS04 . Equivalent amounts of the reagent were taken in such quantity that a given volume of the resulting ammonium permanganate solution (0.075 M) would correspond to the same volume of cesium chloride solution containing 10.0 mg. of cesium per ml. However, the resulting solution was somewhat more dilute (0.065 M), apparently because of adsorption of the ammonium permanganate on the barium sulfate. The weighed ammonium sulfate was dissolved and transferred quantitatively to a separatory funnel. The weighed barium permanganate was dissolved in a liter beaker, fitted with a propeller-type glass stirrer attached to an electric motor. The ammonium sulfate solution was introduced dropwise into the barium permanganate solution with stirring, This required several hours. After thoroughly rinsing the separatory funnel and glass stirrer, the resulting ammonium permanganate solution containing the precipitated barium sulfate was heated on the steamplate for more than 8 hours. The solution was filtered through a 2 0 0 -ml. glass crucible with sintered glass bottom of medium porosity. After heating on the steamplate for about 24 hours more to reduce the volume, the solution was transferred to a 1 0 0 0 -ml. volumetric flask, and diluted tc the mark. The ammonium permanganate solution was standardized against sodium oxalate and found to have a molarity of 0.065. Therefore 1.16 ml. of this solution was equivalent to 1.00 ml. of a cesium chloride solution containing 10.0 mg. of cesium per ml. Subsequent 10 solutions of ammonium permanganate of higher m olarities were made. These solutions were diluted to prepare solutions of lower molarities. All these solutions of the reagent were stored in brown bottles and kept in the laboratory locker when not in use. PROPIONIC ACID. The propionic acid used was reagent grade. BURETS AND PIPETS. A 5-ml. buret was "nalooted" by applying a 2 water-repellent coating of Nalcote to the inside of the buret and to the outside of the stem. The buret was then calibrated. Later, when it was discovered that the ammonium permanganate solution in the buret reacted with the coating, the Nalcote was removed. The calibrations were thereupon ignored, since highly accurate volumes of that solution were not needed. Two more burets, 25 ml. and 50 m l., were cleaned, but not nalooted. Five pipets were nalootedi 1 ml., 2 ml., 5 ml., 10 ml., and 25 ml. The three smallest were calibrated. FILTER MFDT>. Filter paper could not be used for filtrations, since it reacts with permanganate. Glass filter crucibles were used in the earlier experiments, and glass fiber filter mats in Gooch cruci bles were used thereafter. 2 Trade name for a water repellent by The N&lge Co., Rochester, N.Y. EXPERIMENTS ON PRECIPITATION OF CESIUM PERMANGANATE In the beginning, small volumes of cesium chloride solution, having a concentration of 10.0 mg. of cesium per ml.,were placed in a flask cooled b, an ice bath, and titrated with 0.06b M ammonium permanganate in neutral medium, in h y d ro ch lo ric acid medium, and in ammonium hydroxide medium. Wo precipitate of cesium permanganate was obtained in any of these experiments. Cesium chloride solutions of higher concentration were then titrated by adding slightly more than the stoichimetric volume of 0.065 M ammonium permanganate to the solutions contained in a flask cooled by a salted ice 3 bath . One such solution had a volume of 1.00 ml. and contained 50.0 mg. o f cesium , and another had th e same volume and con tain ed 100.0 mg. Though some cesium permanganate was precipitated, the supernatant liquid retained a purple color up to and beyond the end-point. The two mixtures were filtered through weighed glass crucibles, and the precipitates were washed with ice-cold water. After heating for an hour at 115°C., the crucibles containing the precipitates were cooled and weighed. Table 3 shows the results. Obviously the recovery was far from quantitative. Since precipitation was so incomplete in water solutions, it was decided to try solutions consisting of mixtures of water and organic solvents so as to reduce the solubility of cesium permanganate. One requirement of such solvents was that they be miscible with water. Another was that they not react with permanganate. Obviously methyl or ® The temperature of the solution was -2.1°C., as indicated by the temperature of a flask of water in the salted ice bath. 11 12 ethyl alcohol could not be used because of the ease with which they are oxidized. Acetone and dioxane were tried, but were found to be unsuitable for the same reason. Acetic add was decidedly better, but unfortunately cesium permanganate is appreciably soluble in this solvent. Of all the solvents tried, propionic acid appeared to offer the best possibilities as a medium for precipitation of cesium permanganate and as a wash liquid. TABLE 3 ATTEMPTED RECOVERY OF CESIUM FROM CONCENTRATED SOLUTIONS OF CESIUM CHLORIDE Cesium CsMn0 4 CsMn04 Taken Theoretical Reoovered mg. mg. mg. 50 95 2 1 1 0 0 189 79 To examine the suitability of propionic acid as a medium for preci pitation, two solutions of cesium chloride having volumes of1 . 0 0 m l. and 2 . 0 0 m l., and containing 1 0 . 0 mg. of cesium per ml. were evaporated to dryness. Propionic acid, 1 ml. and 2 ml. respectively, was added to the residuesi and to the resulting solutions, cooled in a salted ice bath, slightly more than the equivalent volumes of 0.065 M ammonium permanganate were added. The preoipitates were filtered into weighed glass filter crucibles, washed with propionic acid, dried for an hour at 115°C., cooled, and weighed. The recoveries as shown in Table 4 are an improvement over those given in Table 3, despite the smaller amounts taken, but they are still not quantitative. 13 TABLE 4 AT TUFT ED RECOVERY OF C ESI TJK FROM A SOLUTION OF CES.aiF CHLORIDE 1 14 PROPIONIC ACID Cesium C sMnO^ C sMn04 Per Cent Taken Recovered Theoretical Recovered mg. mg. mg. 10.0 18.9 11.0 58 20.0 37.9 2 2 .7 60 The effect of varying the volume of propionic acid, with respect to the volume of cesium chloride solution taken, was tested. Seven deter minations on standard solutions (10.0 mg. cesium per ml.) of cesium chloride, varying in volume from 1.00 ml. to 5.00 ml., were made, in which the volume of added propionic acid varied from a half to tv/ice that of cesium chloride solution. To each solution slightly more than the equivalent or theoretical volume of ammonium permanganate reagent was added. The precipitated cesium permanganate was filtered into 4 weighed Gooch crucibles fitted with glass fiber filter mats , washed with propionic acid, dried for an hour at 115°C., cooled, and weighed. The recoveries from these seven determinations varied from 70/i to 88^6, being higher than those of Table 4, but still not quantitative. To study the effect of the presence of propionic acid in an unevaporated cesium chloride solution, three determinations were made using 1 ml., 1 ml., and 2 ml. of standard solutions cesium chloride, to which were added 1 ml., 2 ml., and 2 ml., respectively, of propionic ^ From this point on, all permanganate filtrations were thus made. 14 acid, and a alight excess of ammonium permanganate reagent. The recov eries ranged from 38,4 to 47/o. Also, five standard cesium chloride solu tions varying from 1 ml. to 5 ml. were evaporated to 1 drop; 0.5 ml. to 2 ml. of propionic acid and a slight excess of ammonium permanganate were added, and the recoveries ranged from 74$ to 87$. None of these recoveries were quantitative, but as smaller volumes of propionic acid were used, higher recoveries were usually obtained. Since evaporation to one drop and a volume of reagent amounting to one-and-a-half times the theoretical were found to give nearly quantitative results, these two conditions were maintained in six determinations. Smaller amounts of propionic acid than used before were added to the evaporated volume of standard cesium chloride solution. The cesium permanganate precipi tate was washed with propionic acid, and dried for an hour at 115°C. The results are given in Table 5. It is seen that recoveries (the last three) are higher for smaller volumes of propionic acid than (the first three) for larger volumes. This confirmed the preceding observation and also indicated that possibly no propionic acid should be added to the solution. Other experiments showed that its addition had no advantage. From this point on, the acid was used only as a wash liquid. The effect of a larger excess of ammonium permanganate reagent was tested by using volumes up to three times the theoretical. In these experiments the standard cesium chloride solution was evaporated to 1 drop and no propionic acid was added. The precipitation was carried out in a vessel cooled by a salted ice bath. The cesium permanganate precipitate was filtered off, washed with propionic acid, dried for an hour at 115°C., cooled, and weighed. The recoveries were nearly quantitative as shown by the data of Table 6. 15 TABLE b RECOVERY OB' CESIUM FROL; SOLUTIONS OF CESIUM CHLORIDE EVAPORATED TO 1 DROP, DILUTED Vi IT I; VARIOUS VOLUMES OF PROPIONIC ACID, AND PRECIPI1ATED V.I2: CNE- AND-A-HALF TIMES THE THEORETICAL AMOUNT OF AMMONIUM PERMANGANATE Cesium C2ItbCOOH CsMnOd C sl'r.04 Per Cent Present Added Theoretical Recovered Recovered mg. ml. mg. mg. 10.0 0 .5 18.9 17.8 94 20.0 1.0 37.9 35.1 93 50.0 2 .5 9 4 .7 8 9.4 94 10.0 0.02 18.9 18.4 97 20.0 0 .0 3 37.9 35.8 95 50.0 0 .0 3 9 4 .7 91.3 96 TABLE 6 RECOVERY OF CESIUM FROM A SOLUTION OF CESIUM CHLORIDE EVAPORATED TO 1 DROP AND TREATED WITH AN EXCESS OF AMMONIUM PERMANGANATE Cesium E q uivalent CsMn04 CsMn04 Per Cent Present Volumes o f Theoretical Recovered Recovered mg. 0 .0 6 5 M mg. mg. NH4i:n04 10.0 1 .5 18.9 18.9 100.0 10.0 2 18.9 18.4 9 7 .4 10.0 3 18.9 18.8 9 9 .5 20.0 1.5 37.9 36.3 9 5 .3 20.0 2 37.9 36.4 9 6 .0 20.0 3 37.9 37.9 100.0 50.0 1.2 9 4 .7 9 0 .6 9 5 .6 50.0 2 9 4 .7 92.8 9 8 .0 50.0 3 9 4 .7 9 3.2 9 8 .4 16 Three other determinations, in which the cesium chloride solution was evaporated to dryness before the addition of one-and-a-half times the equivalent volume of the reagent, gave recoveries of 96/,= , 36%, and 9?%. In view of the possibility that cooling of the propionic acid wash liquid might give still iiigher results, seven determinations, with the propionic acid cooled in an ice bath, were made. Four of these determinations with a volume of reagent one-and-a-half times the theoreti cal gave recoveries of 35;■<>, 98%, 97%, and 99/o, and the other three with reagent volumes of seven and one-half times the theoretical gave 96%, 95%, and 98/o. Inasmuch as the cooling of the wash liquid appeared to improve results, the filter crucibles were also cooled over dry ice in all subsequent determinations. As a further means of improving the results by reducing the volume of reagent, a more concentrated solution of 0.324 M ammonium permanganate was prepared. A set of three determinations was made with this more concen trated reagent, and with the filter oruoibles and wash liquid oooled. The apparent recoveries amounted to 110%, 130%, and 151%. These very high results were probably due to crystallization of some of the reagent at the low temperature of precipitation and filtration. STANDARD CONDITION'S. The conditions for quantitative precipitation of cesium, established by the preceding experiments may be called the standard conditions. They were used in a ll subsequent determinations. These conditions arej 1. The cesium chloride solution was not evaporated. 2. No propionic acid was added to the cesium chloride solution. 17 3. The precipitation was done in a vessel cooled by a salted ic e b a th . 4. The filter crucibles were cooled over dry ice. 5. The cesium permanganate precipitate wan washed with 6 ml.-9 ml. of propionic acid, previously cooled in an ice bath. 6. The precipitate was dried for 1 hour at 110°-120°C. A series of determinations on standard cesium chloride solutions containing 10.0 mg. of cesium per ml. were made under these conditions. The results are shown in Table 7. TABLE 7 RECOVERY OF CESIUM PRECIPITATED UNDER STANDARD CONDITIONS Equivalent Per Cent Cesium Recovered From A Volumes of Given Volume Taken 0 .3 2 4 M 1.00 ml. 2.00 ml. 5 .00 m l. NH4Mn04 1 .5 9 8 .4 9 9 .2 9 9 .3 2 9 9 .5 9 9 .5 9 9 .8 3 , 9 8 .5 , 100.0 9 9 .9 f 100.01 5 I 98.4J 102.9 100.7 7 100.0 101.1 101.1 7 .5 9 8 .9 100.3 101.1 9 101.6 101.1 100.8 10 105.3 101.6 100.3 As w ill be seen, the recovery was very satisfactory. Even the highest result (105 • 3>o) is only 0.5 mg. different from the 10.0 mg. cesium taken. A set of determinations on cesium chloride solutions containing 5.0 mg. cesium per ml. were then made, with the volumes of reagent similar 18 to those used in the preceding set of experiments. As shown in Table 8, the results were essentially quantitative. TABLE 8 RECOVERY OF CESIUM FROM A SOLUTION OF CESIUM CHLORIDE CONTAINING 5 .0 mg. CESIUM PER ml. UNDER STANDARD CONDITIONS Equivalent pg,j* Cent ,£esium Recovered From A Volumes of Given Volume Taken 0.3 2 4 M NH4Mn04 1 .0 0 m l. 2 .0 0 m l. 5 .0 0 m l. 2 9 1 .6 9 8 .9 9 8 .5 3 96.8 9 7 .9 9 8.9 5 96.8 9 5 .8 97.9 7 101.1 102.1 100.8 9 9 8 .9 100.0 99.8 10 101.1 100.5 99.6 To ascertain the lower limit of concentration of cesium for quanti tative precipitation, determinations were made on solutions containing only 2.0 mg. cesium per ml. with volumes of reagent as in Table 8 and with some larger volumes. The results are shown in Table 9. It w ill be seen that the recoveries were not quantitative. It w ill be seen from Tables 6, 7, 8, and 9 that cesium can be precipitated quantitatively from cesium chloride solutions having concen trations of 10 mg. of cesium per ml. and 5 mg. cesium per ml., but not from solutions having a concentration as low as 2 mg. cesium per ml. The lower lim it is therefore somewhere between the last two concentrations. However, by evaporating solutions of lower concentration than 5 mg. of cesium per ml., quantitative precipitations can be obtained. 19 TABLE 9 RECOVERY OF CESIUM FROM A SOLUTION OF CESIUM CHLORIDE CONTAINING 2 .0 my. CESIUM PER m l. UNDER STANDARD CONDITIONS E quivalent Per Cent Cesium Recovered from A Volumes of Given Volume Taken 0 .3 2 4 M 2«4Mn04 1.00 ml. 2.00 ml. 5 .00 ml. 2 13.2 15.8 34.9 5 2 1 .1 2 3 .7 57.7 7 5 2 .6 8 6 .8 8 2 .5 9 76.3 72.4 9 2 .1 10 9 2 .1 9 3 .4 94.2 10 9 2 .1 9 2 .1 8 8 .4 14 7 1 .1 60.5 9 2 .1 16 89.5 86.8 97.4 Various concentrations of ammonium permanganate reagent were used in making additional determinations on 1.00 ml. volumes of standard cesium chloride solution containing 10.0 mg. of cesium. The results of these determinations are assembled in Table 10. The two highest results in Table 10, 10.5 mg. and 10.5 mg., occurring at three times the equivalent volume and at molarities of 0.327 and 0.271 are probably due to the fact that they were obtained in the two experiments in which a reagent of high concentration was refrigerated. At these high concentrations some of the cold reagent may have crystallized with cesium permanganate. That this is the correct explanation is indicated by the fact that particles of solid remained on the sides of the reagent bottle after filtration of the reagent of 0.271 molarity. These particles dissolved when the bottle was rinsed. Except for the highest result and the four low results, the recoveries were satisfactory. 20 TABLE 10 RECOVERY OF CESIUM WITH VARIOUS CONCENTRATIONS OF REAGENT UNDER STANDARD CONDITIONS NH4 Ma 0 4 NH^MnO^ Cesium M olarity Equivalents Recovered mg. 0 .1 8 1 1 .5 9 .8 0 .1 5 9 1 .5 9 .8 0.07S 1 .5 9 .6 0 .5 1 7 2 . 1 9 .8 0 .1 5 9 2 9 .8 0 .0 7 6 2 9 .4 0.073 2 9 .7 0 .0 5 4 2 9 .5 0 .3 2 7 3 10.5 0 .2 7 1 3 10.3 0 .1 6 3 3 1 0 . 2 0.1 6 3 3 1 0 . 1 0 .0 7 3 3 9 .7 0 .0 5 4 3 9 .8 0.0 5 4 3 9 .9 0 .1 6 3 5 1 0 . 2 0 .0 7 3 5 1 0 . 0 0 .0 6 9 5 9 .9 0 .0 5 4 5 9 .7 0 .1 6 3 7 1 0 . 2 0 .0 7 3 7 9 .9 0 .0 5 4 7 9 .5 0 .1 6 3 9 1 0 . 1 0 .0 7 3 9 9 .8 0 .0 5 4 9 9 .5 REPRECIPITATI05 OF CESIUM PERMANGANATE The possibility of reprecipitating the oesium permanganate was investigated. Water at room temperature was tried and found to dissolve very little of the precipitate. Even hot water had little effect. Since earlier experiments had shown that acetone dissolved oesium permanganate 21 to some e x te n t, th a t so lv e n t was tr ie d on a recovered p r e o ip ita te . The acetone di ssclved some of the precipitate, as was shown by the develop ment of a deep permanganate color, but most of the precipitate remained undissolved. Acetone therefore did not appear to be suitable. On trying oxalic acid, it was found that the permanganate could be readily reduced and brought into solution. However, because of the extended time of heating required for the destruction of excess oxalate ion in the solution and because its destruction by hydrogen peroxide was incomplete, the use of oxalic acid for reduction was abandoned. Since hydrochloric acid dissolves cesium permanganate and reduces the permanganate to Mn , that reagent was tried qualitatively on a precipitate of cesium perman ganate. Some hydrochloric acid and a few drops of water were added to the precipitate and the resulting solution was evaporated to dryness. The dried residue containing manganous ion was dissolved in a few drops of water. To oxidize the divalent manganese ion to the quadrivalent state and to remove it by precipitation, ammonium permanganate solution was added. Enough reagent was added to give a perceptible permanganate color to the supernatant liquid, indicating that a ll the manganous ion had been oxidized. The precipitate was filtered off, and washed with water. The washing was continued until the water in the stem of the filter funnel was colorless. Ammonium permanganate reagent was added to the filtrate, and the precipitated cesium permanganate was filtered off and washed with propionic acid. Several quantitative determinations were sim ilarly made on cesium chlorine solutions, and on cesium chloride solutionscontaining rubidium chloride. The results were variable. Some difficulty was experienced in 22 making a quantitative transfer of the reprecipitate to the filter, since a brown precipitate persistently clung to the walls of the precipitating vessel. Because of the variable results, the length of time involved, and the difficulty of transferring the repreoipitate, the possibility of repreoipitation was not investigated further. BEHAVIOR OF AMMONIUM PERMANGANATE REAGENT TOWARD RUBIDIUM CHLORIDE SOLUTIONS To learn the behavior of ammonium permanganate toward rubidium chloride solutions, experiments were tried with various volumes of the reagent under the standard conditions stated previously. A series of experiments were first made on 5.0 mg. of rubidium as its chloride in 1.00 ml. of water. The results are shown in Table 11. The data in the table indicate that all except the first volume of the 0.324 M reagent, twice the theoretical, precipitates too much rubidium for determinations of cesium in the presence of rubidium. Additional experiments with 5.0 mg. of rubidium as its chloride were made with various lower concentrations of reagent. The results of these experiments are shown in Table 12. It w ill be seen that appreciable amounts of rubidium were precipitated under the conditions of three of the experiments. 23 TABLE 11 PRELIMINARY EXPERIMENTS ON BEHAVIOR OF AMMONIUM PERMANGANATE REAGENT TOWARD RUBIDIUM Equivalent Volumes o f RbMn04 RbMnO* Results Cal 0 .3 2 4 M HH4 Mn04 Theoretical Precipitated culated as Rb mg. mg. mg. 2 1 2 . 0 0 .7 0 .3 3 1 2 . 0 1 . 6 0 .7 5 1 2 . 0 4 .8 2 . 0 7 1 2 . 0 7.2 3 .0 1 0 1 2 . 0 7 .7 3 .2 15 1 2 . 0 8 . 6 3*6 2 0 1 2 . 0 9 .1 3 .8 TABLE 12 BEHAVIOR OF REAGENTS OF LOWER CONCENTRATION TOWARD RUBIDIUM NE4 Xn0 4 NH4 Mn04 RbMn04 R e su lts M o la rity E quivalent Precipitated Calculated as Rb Volumes mg. mg. n 0 .0 7 2 €* 0 . 1 0 .0 4 0*163 2 . 6 0 . 1 0 .0 4 0 .0 7 2 2 . 6 0 . 0 0 . 0 0 .0 7 2 3 .8 0 . 0 0 . 0 0 .1 6 3 6 .4 4 .3 1 . 8 0 .0 7 2 6 .4 0 . 0 0 . 0 0 .0 7 2 7 .8 0 . 2 0 . 1 0 .3 2 4 1 0 7 .7 3 .2 0 .1 6 3 1 1 .5 8 .7 3 .3 0.072 11.5 0 . 2 0 . 1 24 If a smaller amount of rubidium (3.0 mg.) is used, a larger volume of reagent or a reagent of higher concentration may be used. Table 13 shows that at least nine times the equivalent volume causes no signifi cant precipitation, and some of the results obtained with higher propor tions of reagent are still satisfactory. TABLE 13 PRELIMINARY EXPERIMENTS ON BEHAVIOR OF REAGENT TOWARD LOWER CONCENTRATIONS OF RUBIDIUM Equivalent Volumes of RbMn0 4 RbMn04 R e su lts 0 .3 2 4 M NH4 Mn04 Theoretical Preoipitated Calculated as Rb mg. mg. mg. 2 7.3 0 . 2 0 .0 8 3 7 .3 0 . 1 0 .0 4 5 7 .3 0 .3 0 . 1 7 7.3 0 .3 0 . 1 9 7 .3 0 .3 0 . 1 1 0 7 .3 3 .9 1 . 6 1 0 7 .3 0 . 0 0 . 0 15 7 .3 0 .5 0 . 2 2 0 7 .3 3 .1 1.3 2 0 7 .3 1 . 2 0 .5 Additional experiments on 3.0 mg. of rubidium as its chloride were made with various lower concentrations of reagent. The results of these experiments are assembled in Table 14. It w ill be seen that in six of the experiments too much rubidium is precipitated. 25 TABLE 14 BEHAVIOR OF REAGENTS OF LOWER CONCENTRATION TOWARD LOWER CONCENTRATIONS OF RUBIDIUM NH4 ttn04 NH4 Mn0 4 RbMn0 4 R e su lts M olarity Equivalent Volumes Precipitated Calculated as Rb mg. mg. 0 .5 1 7 3 4 .3 1 . 8 0 .3 0 3 3 .2 2 .7 1 . 1 0 .2 3 5 3 .2 1 .5 0 . 6 0 .1 8 1 3 .2 0 . 2 0 .0 8 0.159 3 .2 0 . 0 0 . 0 0.076 3 .2 0 . 0 0 . 0 0.159 4 .2 0 . 1 0 .0 4 0.0 7 3 4 .2 0 . 0 0 . 0 0 .5 1 7 4 .3 5 .0 2 . 1 0 .2 7 1 6 .3 1 .4 0 . 6 0 .0 7 3 6 .3 0 . 0 0 . 0 0.3 3 5 1 0 .5 7.9 3 .2 0.1 4 8 10.5 0 . 0 0 . 0 0.0 9 5 10.5 0 . 0 0 . 0 0.0 7 3 10.5 0 . 2 0 .0 8 0 .1 6 3 14.8 0 . 0 0 . 0 0 .0 9 6 14.8 0 . 0 0 . 0 0.073 14.8 0 . 0 0 . 0 0.1 6 3 18.9 0 . 0 0 . 0 0.073 18.9 0 . 2 0 .0 8 BEHAVIOR OF AMMONIUM PERMANGANATE REAGENT TOWARD POTASSIUM CHLORIDE SOLUTIONS To learn the behavior of ammonium permanganate reagent toward potassium, exoeriments were made on chloride solutions containing 50.0 mg. and 10.0 mg. of potassium with various volumes and concentrations of reagent. The results for 50.0 mg. of potassium are given in Table 15. It w ill be seen that precipitation occurred only under the conditions of the last three experiments. 26 TABLE 15 BEHAVIOR OP AMMONIUM PERMANGANATE REAGENT TOWARD POTASSIUM NH4 Mn0 4 NH4 Mn04 KMn04 R e su lts M olarity Equivalent Volumes Precipitated Calculated as Potassium mg. mg* 0.163 0 . 1 2 0 . 0 0 . 0 0.054 0 . 1 2 0 . 0 0 . 0 0 .0 5 4 0.18 0 . 0 0 . 0 0.163 0 .2 9 0 . 0 0 . 0 0.054 0 .2 9 0 . 0 0 . 0 0 .1 6 3 0 .5 3 0 . 0 0 . 0 0 .0 5 4 0 .5 3 0 . 0 0 . 0 0.324 1 19.0 4 .7 0.324 2 2 .7 0 .7 0.324 3 1 . 0 0 . 2 It is interesting to note that the weights of the three precipitates decrease as the volumes of the 0.324 M reagent increase, undoubtedly due to the increase in total volume of solution. If a smaller amount of potassium is present, a larger volume of reagent or a reagent of higher concentration may be used. The results of experiments on 10.0 mg. of potassium are shown in Table 16. The table shows that an appreciable amount of potassium was precipitated in only one experiment. 27 TABLE 16 BEHAVIOR OF REAGEKT TCWARD LOT/ER CONCENTRATIONS OF POTASSIUM NH4Mn04 KMn04 NH4Mn04 Results Molarity Equivalent Volumes Precipitated Calculated as mg. Potassium m6- \ 0.163 0.59 0.0 0.0 o .o a i 0.59 0.0 0.0 0.081 0.88 0 .1 0.02 0.324 1 0 .1 0.02 0.078 1.42 0.0 0.0 0.335 1.47 0.1 0.02 0.148 1.47 0.0 0.0 0.095 1.47 0.0 0.0 0.081 1.47 0.2 0.04 0.078 1.47 0 .1 0.02 0.077 1.47 0 .1 0.02 0.096 2.05 0 .0 0.0 0.165 2.6 0.0 0 .0 0.324 2.9 0 .3 0.07 0.324 5 2.4 0.6 EXPERIMENTS OH PRECIPITATION OF CESIUM PERMANGANATE IN THE PRESENCE OF RUBIDIUM With a newly-prepared reagent, diluted to varicus concentrations, determinations on standard solutions of cesium chloride containing rubidium chloride were made. Table 17 shows the apparent recovery of cesium and the corresponding precipitation of rubidium from1 . 0 0 ml. of a standard solution of cesium chloride, containing 5.0 mg. of rubidium as xhe chloride. Obviously rubidium was precipitated along with the cesium in a ll these experiments, though in three of them the amount of cc—precipitation was apparently very' small. 28 TABLE 17 APPARENT RECOVERY OF CESIUM FROM A STANDARD SOLUTION OF CESIUM CHLORIDE CONTAINING RUBIDIUM CHLORIDE NH^MnO^ 4 4 NH4 Mn0 4 NH Mn0 Apparent RbMn0 4 RbMn0 4 M olarity E quivalent E quivalent Cesium Probably C alculated Volumes Volumes Recovered Precipitated as Rubidium fo r Cesium for Rubidium mg. mg. mg. 0.0 7 2 1 .5 1 .9 1 0 . 2 0 .4 0 . 2 0 .0 7 2 2 2 . 6 10.9 1 .7 0 .7 0 .0 5 4 2 2 . 6 1 0 . 2 0 .4 0 . 2 Q 0 .0 7 2 3 WWW 11.5 2 .9 1 . 2 0 .0 5 4 3 3 .9 1 0 . 6 1 . 2 0 .5 0 .0 7 2 5 6 .4 10.9 1 .7 0 .7 0 .0 7 0 5 6 .4 11.3 2 .4 1 . 0 0 .0 5 4 5 6 .4 1 0 .7 1 .4 0 . 6 0.0 7 2 7 9 .0 1 1 . 0 1 . 8 0 . 8 0 .0 5 4 7 9 .0 1 0 .5 1 . 0 0 .4 0 .0 7 2 9 1 1 . 6 1 1 .3 2 .5 1 . 0 0 .0 5 4 9 1 1 . 6 1 0 . 2 0 .4 0 . 2 Tables 18 and 19 show the apparent recovery of cesium and the oorre^ spending precipitation of rubidium from 1 . 0 0 ml. of a standard solution of cesium chloride, containing 3.0 mg. of rubidium as the chloride. It w ill be seen that more rubidium is precipitated with reagents of higher molarities than with those of lower m olarities. In most of the determina tions at the higher molarities the amount of rubidium precipitated is more than 0.4 mg.; in most of those at lower molarities it is less than 0.4 mg. 29 TABLE 18 APPARENT RECOVERY OF CESIUM FROM A STANDARD SOLUTION OF CESIUM CHLORIDE CONTAINING SMALLER AMOUNTS OF RUBIDIUM CHLORIDE NH4 Mn04 NH4 Mn0 4 NH4 Mn0 4 M olarity E quivalent E quivalent Apparent RbMn04 RbMn04 Volumes Volumes Cesium Probably C alculated fo r Cesium for Rubidium Recovered Precipitated as Rubidium me. mg. mg. 0 .1 5 9 1 .5 3 .2 1 0 . 6 1 . 2 0 .4 0 .1 5 9 1 .5 3.2 1 0 .5 0 .9 0 .4 0 .1 6 3 2 4 .2 1 1 . 2 2 . 2 0 .9 0 .1 5 9 2 4 .2 1 1 .5 2 .9 1 . 2 0 .3 2 7 3 6 .3 1 3 .1 5 .9 2 .4 0 .2 7 1 3 6 .3 13.2 6 . 1 2 .5 0 .0 9 5 3 6 .3 1 0 . 8 1 .5 0 . 6 0 .1 6 3 5 10.5 1 2 . 6 5 .0 2 . 1 0 .0 9 5 5 1 0 .5 1 0 .9 1 . 6 0 .7 0 .0 9 5 7 1 4 .7 1 1 . 0 1 . 8 0 .7 0 .1 6 3 9 19 1 2 .9 5 .4 2 . 2 0 .0 9 5 9 19 1 0 . 6 1 . 2 0 .4 30 TABLE 19 APPARENT RECOVERY OF CESIUM FROM A STANDARD SOLUTION OF CESIUM CHLORIDE CONTAINING SMALLER AMOUNTS OF RUBIDIUM CHLORIDE NE4 Mn04 NH4 Mn04 NH4 Mn04 Molarity E quivalent E quivalent Apparent RbMn04 RbMnC'4 Volumes Volumes Cesium Probably C alcu lated fo r Cesium for Rubidium Recovered Precipitated as Rubidium mg. mg. mg. 0 .0 7 6 1 .5 3 .2 1 0 . 2 0 .3 0 . 1 0 .0 7 3 2 4 .2 1 0 . 0 0 . 0 0 . 0 0 .0 5 4 2 4 .2 9 .9 0 . 0 0 . 0 0 .0 7 3 3 6 .3 1 0 .4 0 .7 0 .3 0.069 3 6.3 10.4 0 . 8 0 .3 0 .0 5 4 3 6 .3 1 0 . 0 0 . 0 0 . 0 0.073 5 10.5 10.3 0.5 0 . 2 0 .0 7 0 5 10.5 10.3 0 .5 0 . 2 0 .0 6 9 5 1 0 .5 1 0 .4 0 .7 0 .3 0 .0 6 9 5 10.5 10.5 0 .9 0 ,4 0 .0 5 4 5 1 0 .5 1 0 .4 0 . 8 0 .3 0 .0 7 3 7 1 4 .7 1 0 . 6 1 . 2 0 .4 0 .0 6 9 7 1 4 .7 1 0 . 2 0 .3 0 . 1 0 .0 5 4 7 1 4 .7 1 0 . 0 0 . 0 0 . 0 0 .0 7 3 9 19 10.3 0 .5 0 . 2 0 .0 6 9 9 19 1 0 . 1 0 . 2 0 .0 8 0 .0 5 4 9 19 1 0 . 2 0 .3 0 . 1 EXPERIMENTS ON PRECIPITATION OF CESIUM PERMANGANATE IN THE PRESENCE OF POTASSIUM Experiments with various volumes of the reagent were made on 1.00 ml. of standard cesium chloride solution containing potassium chloride. Table 20 shows the recovery of cesium in the presence of 50.0 mg. of potassium as its chloride. It is seen that there is no apparent co-precipitation of potassium, though the recovery of the cesium is not very good, possi bly because the high ion concentration in the solution increases the solubi lity of cesium permanganate. TABLE 20 RECOVERY OF CESIUM FROM A STANDARD SOLUTION OF CESIUM CHLORIDE COST ASKING POTASSIUM NH4 Mn0 4 NH4 Mn0 4 NH4 Mn04 KMCO4 M olarity E quivalent E quivalent Cesium KMn0 4 C a lcu la ted Volumes Volumes for Recovered Precipitated as Potassium fo r Cesium Potassium mg. mg. mg. 0.0 5 4 2 0 . 1 2 9 .5 0 .0 0 . 0 0.0 5 4 5 0 .2 9 9 .6 0 . 0 0 . 0 0.054 9 0.53 9.5 0.0 0 . 0 Table 2 1 shows recovery of cesiumin the presence of 1 0 . 0 mg. o f potassium as the chloride. It is seen that there is little or no apparent oo-preoipitation of potassium, and that the recovery of cesium is satisfac tory. Evidently the ion concentration is not too high in this solution. 32 TABLE 21 RECOVERY 01 CES'UM FROM A STANDARD SOLUTION OF CESIUM CHLORIDE CC.'fTAINING SMALLER AMOUNTS OF POTASSIUM NH4Mn04 NB4Mn04 lvE4Mn04 KMnCi Molarity Equivalent Equivalent Cesium KMn04 Calculated V 01 UlTaO 3 Yclumes Recovered Precipitated as Pot as si un fo r Cesium fo r Potassium mg. mg. ag. 0.163 2 0.59 10.0 0 .0 0 .0 0.054 2 0.59 9.5 0.0 0.0 0.163 5 1.46 10.2 0.4 0 .1 0.054 5 1.46 9.5 0.0 •''n 0.163 9 2.64 10.3 0.6 0 .1 0.054 9 2.64 9.7 0.0 0 .0 Five datermioations for 50.0 mg. of cesium in 1 ml. of water with a reagent of 0.10 molarity were made. Two of the cesium solutions contained rubidium, one contained potassium, and one contained both rubidium and potassium. The results are shown in Table 22. It will be seen that the recovery of the cesium was satisfactory. 33 TABLE 22 RECOVERY OF CESIUM FROM A CONCENTRATED SOLUTION DI CES TUM CHLORIDE CONTAINING OTHER ALKALI CHLORIDE NH4 Mn04 NH4 Mn04 NH4 Mn04 M olarity E quivalent E q uivalent Other Alkali Apparent Cesium Volumes Volumes Taken Recove red fo r Cesium for Rubidium mg. or K 0.103 1.5 49.3 0 .1 0 3 1.5 15.8 3 .0 mg. Rb 5 0 .2 0 . 1 0 1 1.5 9 .6 5 .0 mg. Rb. 5 0 .3 0 . 1 0 1 1.5 0 .4 4 5 0 .0 mg. K 4 9 .2 ( 9 . 6 5 .0 mg. Rb.'l 0 .1 0 3 1 .5 5 0 .0 { 0 .4 4 5 0 .0 mg. K / DETERMINATION OF CESIUM BY A VOLUMETRIC METHOD Four determinations were made on 1.00 ml. of standard cesium chloride solution. Instead of the cesium permanganate precipitate being weighed, 2 . 0 0 ml. of standard oxalic acid was added to it, together with, sulfuric acid. The excess oxalic aoid was titrated with standard ammonium perman ganate reagent contained in a micro buret, and the cesium was calculated from the volume of oxalic acid needed to react with the cesium permanganate. The results, which are shown in Table 23, were found to be satisfactory. 34 TABLE 23 VOLUMETRIC ESTIMATION OF CESIUM 2iH4 Mn0 4 NH4 MNO4 H2C2°4 H2 c2°4 Cesium Cesium M olarity M olarity Volume Volume Taken Recovered ml. ml. mg. mg. 0 .1 5 5 0.0570 2 . 0 0 1.30 1 0 . 0 9 .9 0.155 0.0570 2 . 0 0 1.30 1 0 . 0 1 0 . 2 0 .1 5 5 0.1006 2 . 0 0 0 .7 5 1 0 . 0 1 0 . 0 0.155 0.1006 2 . 0 0 0 .7 5 1 0 . 0 1 0 . 0 STABILITY OF AMMONIUM PERMANGANATE REAGENT At one point during the experiments, a check determination on the 0.324 M ammonium permanganate solution being used as reagent gave a cesium recovery of only 32 per cent. It was suspected that this solution was partially decomposed. Another check determination with the 0.324 M ammonium permanganate solution taken directly from the reserved stock bottle gave a recovery of 82 per cent. This not only showed that the stock solution was the better of the two, but that ammonium permanganate solution may decompose extensively. Thereafter, the reagents that were being used were standardised rather frequently. In Table 24 are listed the results of such check standardisations for nine different reagents of various molarities treated in various ways. All these standardisations were against pure sodium oxalate. 35 TABLE 24 STABILITY Of AMMONIUM PERMANGANATE SOLUTIONS Elapsed Time M olarity Treatment Days Reagent 1 0 0.3 0 3 Reagent at 4 0.2 9 9 room temperature. Reagent 2 0 0.0761 Reagent 1 1 0.0730 a t room 18 0.0721 temperature. Reagent 3 0 0 .2 6 8 Reagent 1 0 .2 7 1 refrigerated. 5 0 .2 6 4 Filtered before 8 0 .2 6 4 standardizing. Reagent 4 0 0 .1 6 7 Reagent refrigerated. Filtered 9 0.167 before standardizing. Reagent 5 0 0 .1 6 3 9 0 .1 6 3 Reagent refrigerated. Filtered before standardizing. Reagent 6 0 0.0948 Reagent refrigerated. 2 0 .0 9 5 7 Filtered before 3 0.0949 standard!zing. Reagent 7 0 0.0696 Reagent refrigerated. Filtered 1 0.0693 before standardizing. TABLE 24 (CONTINUED) Elapsed Time Molarity Treatment Days Reagent 8 0 0.0575 Reagent 3 0.0570 refrigerated. 8 0.0570 Filtered before 19 0.0565 standardizing. Reagent 9 0 0.0543 Reagent 3 0.0541 refrigerated. 4 0.0544 F ilte r e d 6 0.0541 b efo re 1 0 0.0539 standardizing. 37 It w ill be seen that the reagents kept at room temperature were less stable than those kept aba low temperature. For the purpose of precipitating cesium the changes in the molarities of those of this second group are insignificant over the periods listed. However, ammonium permanganate solutions cannot be relied upon to remain unchanged over periods of many weeks, even when kept at a low temperature. F il tration to remove any solid decomposition products is a necessary step for satisfactory results either in standardizing these solutions or in using them for the determination of cesium. . GENERAL DISCUSSION Cesium may be precipitated quantitatively from a chloride solution containing 5 mg. to 50 mg. of cesium per ml. by ammonium permanganate reagent of any molarity from about 0.05 to about 0.32, provided this is done near 0°C. The volume of reagent may be as small as 1.5 times or as large as 9 times the theoretically equivalent volume, as demonstrated by the data of Tables 7, 8 , and 10. Rubidium alone in amounts up to 5 mg. was not precipitated when the concentration of the ammonium permanganate was not too high (Tables 11 and 12). Rubidium in amounts up to 3 mg. was not precipitated, even with a rather concentrated reagent (Tables 13 and 14). The maximum allowable volumes and molarities are given in Table 25. Potassium alone in amounts up to 50 mg. was not precipitated at any, bur the highest, concentration of reagent (Table 15). In amounts up to 1 0 mg., potassium was not precipitated at any, including even the highest, 38 concentration of the reagent, except with a large volume of the most concentrated reagent (Table 16). The maximum allowable volumes and molarities are given in Table 25. TABLE 25 MAXIMUM VOLUMES AM) KOLAPJTIES OF AMMONIUM PERMANGANATE REAGENT ALLOWED WITHOUT PRECIPITATING ONE ALKALI ALONE IN A CHLORIDE SOLUTION Maximum NH4 Mn0 4 NH4 Mn0 4 NH4 Mn04 Amount o f M olarity Equivalent Volumes Equivalent Volumes A lk a li fo r 1 0 mg. For Rubidium or K Cesium 5 mg. Rb. 0.16 2 2 . 6 5 mg. Rb. 0 .0 7 9 11.5 3 mg. Rb 0.16 9 18.9 3 mg. Rb 0 .3 2 4 .3 9 50 mg. K 0 .1 6 9 0 .5 3 1 0 mg. K 0 .3 2 9 .9 2 .9 Cesium in amounts between 5 mg. and 50 mg. can be precipitated quanti tatively by ammonium permanganate reagent in the presence of not more than 3 mg. of rubidium and of not more than 50 mg. of potassium, provided that the concentration of the reagent is kept as small as about 0.10 M and the volume is 1.5 times the equivalent (Tables 17, 18, 19,20, 21, and 22). RECOMPILED PROCEDURE On the basis of the results of all the experiments the following procedure may be recommended for the determination of oesium. Evaporate 39 t o dryne3 3 in a 50-ml. Erlenmeyer flask the solution of chlorides con ta in in g between 5 mg. and 50 mg. o f cesium , not more than e.a equal amount o f potassium , and not more than 3 mg. o f rubidium. D isso lv e th e residue in 1 ml. of water. Place the flask containing the solution of alkali chlorides in a salted ice bath, and slowly add from a buret 6 ml. of cold freshly filtered 0.10 M ammonium permanganate reagent while swirling the solution in the flask. Allow the flask to remain in the ice bath for 10 minutes. During this time cool a weighed Gooch cruoible, provided with a glass filter mat, over dry ice, and cool some propionic acid vdth an ice bath. After the flask, cruoible, and vessel containing the propionic aoid have been cooled, filter the precipitate with suction into the cold crucible fitted to a funnel in a filter flask. Rinse the flask and wash the precipitate with 6 ml. to 9 ml. of the cold propionio aoid. Allow the suction to continue until the precipitate appears to be dry. Remove the excess of propionic aoid adhering to the bottom of the cruoible by pressing the crucible on an absorbing medium which leaves no lint, such as a paper towel. Heat the cruoible with the precipitate for an hour at 110° - 120°C. After cooling the cruoible in a desiccator for at least 40 minutes, vwigh the crucible with the precipitate. From the weight of the precipitate calculate the weight of cesium, cesium chloride, or cesium oxide. The factors are; for cesium, 0.5278; for cesium chloride, 0.668S; for cesium oxide, 0.5593. To use the volumetric method, instead of weighing the precipitate, dissolve it with small portions of hot water, and transfer each successive solution to a 150 ml. beaker, containing a hot (80° - 90°C.) solution of 40 5.00 ml. of 0.25 M oxalic acid and 2 ml. of concentrated sulfuric aoid. Then with a scoopula transfer the mat with remaining precipitate. After all the permanganate is reduced, titrate the excess of oxalate in the hot s o lu tio n w ith 0.1CD0M anmonium permanganate so lu tio n . S im ila r ly add 2 ml. of concentrated sulfuric aoid to 5.00 ml. of the 0.25 M o x a lic acid solution, heat the solution to 80° - 90°C., and titrate. Using to represent the volume of ammonium permanganate in the first titration and V 2 "to represent the volume of ammonium permanganate in the second titration, calculate cesium, cesium chloride, or cesium oxide by one of the following equations* mg. Cs * (V 2 - Vx) X 0.1000 X 132.91 mg. CsCl = (V2 - Vx) X 0.1000 X 168.37 mg. Cs20 = (V2 - Yx) X 0.1000 X -2-~ V 7? NOTES ON PROCEDURE 1. If it is known that the solution of chlorides contains more than 50 mg. of cesium, the solution may be evaporated if necessary, transferred to a volumetric flask, diluted to the mark, and an aliquot used for the determination of cesium. 2. The dilute (0.10 M) reagent should be filtered once each day that it is used, immediately prior to standardization and prior to any determinations. An unweighed Gooch crucible fitted with 2 glass fiber filter mats has been found to remove the precipitated manganese dioxide. A second filtration through another crucible is made. If, after the manganese precipitates are washed with water, anything more than a yellow 41 discoloration is present on the 3©cond mat, a third filtration is recommended. Usually two are sufficiant. 3. In order cool the filter crucibles over dry ice, a half gallon Dewar flask was fitted with a thin aluminum plate with legs, so that the plate rested about 4.5 cm. from the top of the flask. The plate contained 4 holes of such size as to support a cruoible in each. Crushed dry ice was introduced through these holes to within about 3 cm. of the plate, and the Dewar was covered with a lid. 4. The propionic acid wash liquid may be conveniently cooled in a small graduated cylinder placed in an 800 ml. beaker filled with crushed ice. No salt is added to this ice bath. 5. It is well to wear a rubber glove to handle the flask and the graduated cylinder as a protection against the corrosive aotion of the propionic acid. Place a small glass oup or beaker over the cylinder of propionic aoid to prevent volatilization of the acid. 6 . If the volumetric method is used, the ammonium permanganate reagent should be at room temperature during its standardization and during the titration of the oxalic acid. SUMMARY By reacting aximonium sulfate with barium permanganate, and filterin g off the precipitated barium eulfate, a solution of ammonium permanganate is obtained. After the solution is diluted and refrigerated, the ammonium permanganate is a satisfactory reagent for the separation of moderate amounts of cesium from small amounts of rubidium and from large amounts of potassium and for the gravimetric determination of cesium in the presence of such amounts of rubidium and potassium. The reagent gives quantitative results, if it is not too concentrated, and if the preci- o pitation is made near 0 C. The gravimetric determination of cesium as the permanganate by this reagent is more rapid than t-y any previously published methods. The volumetric determination of cesium, by dissolving the cesium permanganate precipitate with an excess of oxalic acid and titrating the excess of acid with standard permanganate, is even more rapid, inasmuch as the time required for these operations is less than that needed for drying, cooling, and weighing the cesium permanganate precipitate. BIBLIOGRAPHY 1. Baxter, G. P., Boylston, A. C., and Hubbard, R. A., "The Solubility of Potassium Permanganate," 28, 1336 (1906). 'W v v 2. Duval, Clement, "Inorganic Thermogravimetric Analysis," Elsevier Publishing Co., New York, 1953, pp. 305, 391. 3. Hillebrand, W. F., Lundell, G. E. F., Bright, H. A., and Hoffman, J. I ., "Applied Inorganic Analysis," John Wiley & Sons, Inc., New York, 1953, p. 646. 4. Hillyer, J. C., "Determination of the Common and Rare Alkalies," Ind. Eng. Chem. , Anal. Ed., 9j 236 (1937). 5. Kolthoff, I. M., and Sandell, E. B., "Textbook of Quantitative Inorganio Analysis," The Macmillan Co., New York, 1949, pp. 358, 373. 6. Noyes, A. N., and Bray, W. C., "A System of Qualitative Analysis for the Rare Elements," The Maomillan Co., New York, 1927, p. 245. 7. O'Leary, W. J. and Papish, J., "Analytical Reactions of Rubidium and Caesium," Ind. Eng. Chem. , Anal. Ed., J6, 107 (1934). 8. Patterson, A. M., "Solubilities of Permanganates of the Alkali Metals," J. Am. Chem. Soo. , 28,1734(1906). 9. Schoeller, W. R., and Powell, A. R., "The Analysis of Minerals and Ores of the Rarer Elements," 2d ed., Charles Griffin & Co., London, 1940, p. 41. 10. Wells, R. C., and Stevens, R. E., "Determination of the Common and Rare Alkalies in Mineral Analysis," Ind. Eng. Chem., Anal. Ed., j6, 439 (1934). 11. Wells, R. C., and Stevens, R. E., "The Ainalysis of Pollucite," Ind. Eng. Chem., Anal. Ed., 9, 236 (1937). 43 AUTOBIOGRAPHY I, Wallace E. Beebe 1, was born in Ringtown, Pennsylvania, September 18, 1904. I received my secondary school education in the public schools of Ringtown. In 1923 I was graduated from Keystone State Normal School, now called Teachers College, Kutztown, Pennsylvania. After further undergraduate work at Muhlenberg College I received the Bachelor of Arts degree in 1929. I received the Master of Education degree from Rutgers University in 1933, and the Master of Science degree from The Ohio State University in 1952. I served as an assistant in the Department of Chemistry at Ohio State while I was completing the requirements for the degree Doctor of Philosophy. 44