SOLUBILITY OF THORIUM KITRATE TETRAHY DRATE
1441
GOLDFINGER, G., M A R K , H . , AND S I G G I A , S.: Ind. Eng. Chem. 36, 1083 (1943). H E S S , K., A N D TROGUS, C.: Z.physik. Chem. BlS, 157 (1931); Kolloid-2. 68, 168 (1934). LUERS, H . : Z. angew. Chem. 43, 455 (1930); 46, 399 (1932). NEUMAN, J . : Dissertation, Polytechnic Institute, Dresden, 1910. KICKERSON, R . F . : Ind. Eng. Chem., Anal. Ed. 13, 423 (1941); Ind. Eng. Chem. 33, 1022 (1941); 34, 85, 1480 (1942). (11) PACSU, E . , AND COWORKERS: Textile Research J. 16, 243, 318, 490, 5M (1946). (12) SAEYAB, J. F . : Ind. Eng. Chem. 37, 43 (1945). (13) SAEMAN, J. F., BUBL,J. L . , . ~ N DH A R R I S , E. E . : Ind. Eng. Chem., Anal. Ed. 17, 35 (6) (7) (8) (9) (10)
(1945). (14) SAEMAN, J. F . , H A R R I S , E. E . , (1945).
AND
KLIBE,A. A , : Ind. Eng. Chem., Anal. Ed. 17, 95
(15) SCHAFFER, P. A,, ABD SOMOGYI, 9.: J. B i d Chem. 100, 695 (1923). G . V., A X D LOHMAN, H . J . : J. prakt. Chem. 167, 238 (1941). (16) SCHULTZ, (17) STAYM, A. J., AND COHEN,W. E.: J. Phys. Chem. 42, 921 (1938). (18) WOLFROM, M. L., AND COWORKERS: J. Ani. Chem. Soc. 69, 282 (1937); 60, 1026, 3009 (1938); 61, 1072 (1939).
T H E SOLUBILITY OF THORIUM XITRATE TETRAHYDRATE I N ORGANIC SOLVESTS AT 25OC.l CHARLES C . TEMPLETON
AJD
NORRIS F. HALL
Depaitment of Chemistry, University of Wisconsin, Madison, Wisconsin Received July 14, 1947
Preliminary t o research into the liquid-liquid extraction of thorium salts from aqueous solutions, an investigation has been made of the solubility of thorium nitrate tetrahydrate in a wide range of organic solvents. No such comprehensive study has been previously reported. Misciattelli (4) made a complete study of the system thorium nitrateAiethy1 ether-water. Wells ( 5 ) measured the ether solubilities of the nitrates of thorium, zirconium, and seven of the rare earths t o determine if they interfered with a method of Hillebrand (1) for dissolving uranyl nitrate in ether t o separate from it the last traces of the rare earths. Imrie (2) extracted thorium nitrate from aqueous solution with ether, and Misciattelli (3) used ether to extract uranyl nitrate from an aqueous nitric acid solution also containing thorium. The solubility of the tetrahydrate, rather than that of the anhydrous salt, was investigated because it was desired t o use the data t o make qualitative predictions concerning extraction from aqueous solution. The anhydrous salt was prepared in Misciattelli's work, but it was necessary t o use nitrogen pentoxide. 1 This paper is based upon the thesis submitted by C. C. Templeton to the Graduate Faculty of the University of Wisconsin in partial fulfillment of the requirements for the degree of Master of Science, April, 1947. Presented before the Meeting-in-Miniature of the Wisconsin Section of the American Chemical Society, April 26, 1947.
1442
CHARLES C. TEMPLETOX APiD NORRIS F. HALL EXPERIMEhT4L
Materials Thorium nitrate tetrahydrate, Baker’s C.P. Analyzed, was used for all solutions. The various organic liquids were in each case of Eastman Kodak Company “practical’’ grade or of better purity. No further purifications were made because of the desire t o investigate a large number of solvents in a reasonable length of time. Method Suitable amounts of thorium nitrate tetrahydrate and solvent were mixed in a 6-in. test tube. The corked tube was tied with string and sealed with DeKhotinsky cement. Agitation, end over end, in a specially constructed device rotating at 35 R.P.M., was begun immediately in a 25’C. =t0.05’ water thermostat and continued for 5 days. After the solution had settled, a portion was pipetted into a platinum crucible for weighing. The covered crucibles were heated with a small flame t o evaporate or burn away the solvent. Later, ignition t o thorium dioxide was made. Solubilities mere calculated as grams of anhydrous thorium nitrate per 100 g. of solution. Separate experiments showed the evaporation losses on weighing t o be less than 0.25 per cent for any solvent boiling above 8O’C., and negligible with respect t o the usual gravimetric errors for solvents boilihg above IOO’C. The gravimetric errors amounted t o less than 0.2 per cent. The method of approaching equilibrium was settled upon after an extended study of the effects of time, agitation, and heating upon the solubility and the stability of the solutions. It was immediately apparent that wide temperature ranges could not be used because of the evolution of gases from the solutions, and also that a long period of continuous agitation was necessary t o get the nitrate into solution. Solutions in isoamyl alcohol, propiophenone, and ethyl butyrate were agitated for over 20 days a t 25’C., with periodic determinations of the solubility, in order t o investigate the effects of isothermal agitation. For the alcohol and ketone, the solubility was constant after 4 days. No signs of instability had been noted in the alcohol solution after 24 days of continuous agitation; the ketone solution showed gas evolution only on the eighteenth day. The ester solution, however, never attained a constant solubility. An upward inflection point in the solubility-agitation-time curve was noted on the fourteenth day, along with the first evolution ot gas. Afterward the solubility continued t o increase until the twentieth day, when the gas pressure became great enough t o break the cement seal. From the above it was concluded that equilibrium could be reached by isothermal agitation for all the solvents other than esters. That equilibrium \vas attained by this method was actually demonstrated in the case of methyl isobutyl ketone by preparing four different solutions with varying propoitions of solvent and nitrate. All yielded results which averaged at 42.20, the total spread being only 0.15.
1443
SOLUBILITY OF THORIUM SITRATE TETRAHYDRATE
The conventional method of approaching equilibrium from both a higher and a lower temperature was not applicable here because of the small change of the solubility with temperature. For isoamyl alcohol, methyl isobutyl ketone, methyl n-amyl ketone, and methyl n-hexyl ketone, the values at 25°C. and 35°C. differed by less than 0.5 per cent. TABLE 1 Solubztztaes of thorium nitrate tetiahzldrate in selected extractzon solvents at 26°C. 3.z 0 06" SOLVENT
!
Th(KO& PER 100 G . OF S0L U II O N
V*IUE
grams
prams
37.05 37.08
37.06
18.59 19.09 19.28 18.73
18.9
Methyl isobutyl ketone, . . . . . . . . . . .
42 13 42.28 42.18 42.20
42.20
Jlethyl n-amyl ketone
36.58 36.80 36.65 36.70
36.68
Methyl n-hexyl ketone
30.85 31.25 31.08
31.06
Isoaiiiyl alcohol . . . . . . . . . . . . . . . . . .
37.85 37.80
37.8
n-IIexyl alcohol. . . . . . . . . . . . . . . . . .
33.64 33.36 33.15
33.4
Diisopropyl ketone. . . . . . . . . . . . . .
I .icetophenone . . . . . . . . . . . . . . . . . . . . .
I l'ropiophenone . . . . . . . . . . . . . . . .
I ~
RESULTS AND DISCUSSIOS
Sixty-five solvents were investigated in all. Table 1 lists the solubilities in eight solvents which are regarded as being promising extraction solvents, owing t o their physical properties. These have been determined from two or more separate solution samples. Table 2 contains most of the other solvents besides esters which showed appreciable dissolving power for thorium nitrate tetrahy-
1444
CHARLES C. TEMPLETON A S D PI'ORRIS F. HALL
TABLE 2 Other soluents (excluding esters) showing appreciable solvent action on thorzum nilrate tetrahydrate at 26'C. & 0.05' Th(KOs)&P E R 100 G . OF SOLC
SOLIEXI
SOLYEXT
TlON
j
Methyl alcohol. . . . . . . . . . . . . . Ethylene chlorohydrin . . . . . . . .
65.7 44.4
n-Butyl alcohol. . . . . . . . . . . . .14.6 Isobutyl alcohol . . . . . . . . . . . . .39.9 Cyclohesanol . . . . . . . . . . . . . . . . .35.9 Benzyl alcohol, , . . , . , , . . , . , . . 20 9 Diethyl e t h e r . . . . . . . . . . . . . . l12:8 Di-n-butyl e t h e r . . . . . . . . . . . 2.69, 0.53,
.I
Diisoamyl e t h e r . . . . . . . . . . . . . 1.12, 0.14, 0.14" Dioxane, . . . . . . . . . . . . . . . . . . . . . 42.9
* Values
determined 1, 2, and 4 days, respectively, after agitation was ceased
TABLE 3 Solvents shouing neglzgible solrent action on thorium nztrate tetrahydrate Tho? PER 100 YL. OF
SOLYF.XYT
grams
hfethylene chloride. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chloroform. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon tetrachloride. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Nitrobenzene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aniline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dimethylaniline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . o-Toluidine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Piperidine.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . rn-Cresol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0.00 0.01
0.05
I
0.02 0.04 0.07
0.09 0.01
0.10
SOLUIIOX
1445
SOLUBILITY O F THORIUM KITRATE TETRAHYDRlTE
drate. These values represent average values from determinations on single solution samples. Tab19 3 gives the solvents which showed negligible solvent action. Table 4 records the highest observed values for the esters and certain solvents which yielded very viscous solutions; it does not contain true equilibrium values. Plots have been made of the solubility, within a homologous series of solvents, as a function of the number of carbon atoms in the solvent molecule. Figure 1 shows ketones and ethers, while figure 2 is for alcohols. The oxygen-containing solvents, in general, dissolved thorium nitrate tetrahydrate appreciably, while the other solvents did not. Thus, the alcohols, TABLE 4 Thorium nitrate solutions i n esters and miscellaneous solvents AIGHTST OBSERVED QU.%?ITIIY OF COMPOSITIOY OF SOLIDIFIED CENT Th(N0ah
SOLVENT
~Tb(XO&pm104 0 . OF SOLUT~ON~SYSTEX:PE; gfami
Ethyl formate.. . . . . . . . . . . . . . . . . . . . Methyl acetate. . . . . . . . . . . . . . . . . . . . Ethyl acetate., . . . . . . . . . . . . . . . . . . . . . . Ethyl propionate, . . . . . . . . . . . . . . . . . . . . . . Ethyl b u t y r a t e . . . . . . . . . . . . . . . . . . . . . Ethyl caproate. . . . . . . . . . . . . . . . . . . . . . . . . Ethyl benzoate,, . . . . . . . . . . . . . . . . Ethyl phenylacetate . . . . . . . . . . . . . . . . . . . Ethyl acrylate. . . . . . . . . . . . . . . . . . . . . . . . .
Solidified
32.5
Approx. 60 .O 43.4 67.1 56.9 28.6 6.3 18.42
75.4
Solidified i0.08 62.26
i
(Just before solidification) Solidified
2.4
-Ethylene glycol.. . . . . . . . . . . . . . . . . . . . . . . . Diethylene glycol.. . . . . . . . . . . . . . . . . . . . . . . . Hexamethylene glycol . . . . . . . . . . . . . . . . . . . Glycerol, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ethylene glycol monomethyl e t h e r . , . . . . Ethylene glycol monoethyl ether. . . . . . . . Cyclohexanone . . . . . . . . . . . . . . . . . . . . . . . . . . Diethyl carbonate. . . . . . . . . . . . . . . . . . . . . . . Isoquinoline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I
.I
I
44.4 47.3 13.5 45.6 59.2 54.6 28.5 8.88
10.5
~
I
~
Very viscous Very viscous Very viscous Very viscous Very viscous Very viscous Solidified Solidified Solidified
ketones, esters, and ethers showed solvent action, while hydrocarbons, halogenated hydrocarbons, nitro compounds, and amino compounds did not. Exceptions are isoquinoline, which does dissolve, and m-cresol, which does not dissolve the nitrate. The solution phenomenon apparently is dependent upon some property of the oxygen-containing grouping in the solvent molecule. Two generalizations may be drawn from the results. First, within a homologous series, the dissolving power decreases with increase in the molecular weight of the solvent. Secondly, the effectiveness of the dissolving group is decreased as the steric hindrance around it is increased. The curve for the methyl ketones in figure 1 illustrates the decrease with in-
1446
CHARLES C. TEMPLETON AND XORRIS F. HALL
creasing molecular weight. The decrease due+to steric hindrance may be seen from a comparison of diisopropyl ketone with methyl n-amyl ketone, which have equal molecular weights. In the case of acetophenone and propiophenone, steric hindrance again comes into play as the decrease caused by an additional -CH*grouping is greater than that caused along the methyl ketone curve where the -CH2-is added at the more distant end of the molecule. The ethers show a much greater decrease in clissolving power with increasing molecular weight than do other solvents. This would be expected, since the values are for a series of symmetrical ethers, the ether linkage being continually more “boxed in” from both sides as methylene groups are added. If R series
NO. OF CARBU’4 ATOMS IN MOLECULE KETONES AND
ETHERS
FIG.1. Solubility of thorium nitrate in ketones and ethers the solvent molecule.
8s a
function of the nature of
of methyl ethers were available, the expected decrease with increasing molecular weight should be less. The decrease in dissolving power with increasing molecular weight for saturated normal alcohols may be seen in figure 2. The solubilities in the is0 alcohols are in each case slightly less than those in their normal isomers. This also may be ascribed to steric hindrance, but when the number of carbon atoms in the alcohol molecule exceeds six, the difference becomes very small. In the latter case, the branching is probably too far away from the hydroxyl group t o affect its properties appreciably. Equilibrium solubilities were not attained for esters by this method, and in fact it appears t o be possible t o prepare by sufficient agitation a solution of
SOLUBILITY OF THORIUM hX'IX.4W TETR.4HYDRATE
>
-
5z
20
3
BENZYL -
9
SOLIOltlCATIOM
z 0
I447
100 -
VALUE
o W I O ~ C S T OBSLRVLO LIOUB
VbWL
.
c
3
80-
5
-
8 60-
-. nz
a
-
0 w
40
L
c
ACCTATL
. . .
20 -
i3
(
-
oLWL
-
0'
3
4 5 NUMBER OF
6 7 CARBON ATOMS PER ESTERS
8 9 MOLECULE
10
FIG.3. Trends of the solubility of thorium nitrate in esters as a function of the nature of the solvent molecule.
1448
CHARLES C. TEMPLETON AND NORRIS F. HALL
thorium nitrate in an ester of any concentration up t o that at which the entire system solidifies. Thus in figure 3 there have been plotted these solidification concentrations, as well as the highest observed liquid concentrations, of several ester solutions against the size of the solvent molecule. The curve represents the limit beyond which liquid solutions cannot be prepared. h s this limit is approached, the solutions become very viscous and show large evolutions of gas. This instability is probably due t o some mechanism involving the hydrolysis of the ester by the water of crystallization of the nitrate as a step. Plots of all these data when expressed as mole ratios or mole fractions exhibit the same trends as those pointed out above for the data espressed as grams of thorium nitrate per 100 g. of solution. Several glycols, glycol ethers, and other miscellaneous solvents were investigated but failed t o give equilibrium solubilities, owing either t o their solutions becoming unmanageably viscous or solid, or t o their exhiljiting very slow rates of solution. A peculiar behavior was noted for the solutions in di-n-butyl and diisoamyl ethers. After the 5 days of agitation was over, the nitrate content of the solution decreased progressively during the first 4 days of standing. This has not been thoroughly investigated, and the highest values have been taken for the solubility comparisons. A wide variety of side phenomena, such as precipitates, color changes, and gas evolution, have been noted for certain of the systems, after they have stood for long periods of time or undergone considerable agitation. These should be interesting subjects for separate investigations. Other work on the solubilities of alkali, calcium, zirconyl, and rare earth nitrates in alcohols and ketones indicates that the use of higher alcohols or ketones (such as n-hexyl alcohol or methyl n-hexyl ketone) t o extract thorium nitrate from aqueous solutions also containing the above cations has a definite probability of success. Work is in progress in this laboratory on such a process and also on the determination of the distribution expressions for thorium nitrate between water and these solvents. SUMMARY
1. Oxygen-containing organic solvents will generally dissolve thorium nitrate tetrahydrate, while other organic solvents will not. Equilibrium may be attained in solutions in alcohols, ketones, and some ethers, but not in esters. 2. Dissolving power decreases with increasing molecular weight of the solvent, and with increased steric hindrance around the oxygen-containing group in the solvent molecule. This research was supported in part by the Research Committee of the University of Wisconsin Graduate School from funds supplied by the Wisconsin Alumni Research Foundation. I n the early phases of the work, Misses Beth Stube and Margaret Susor ably assisted in the analytical work.
OXID.\TION
OF A C L T O I S
REFERENCES (1) I I I L L E R R I S D : C.
S.Geol. Survey Bull. 78, 4 i (1891).
E :anorg. Chern. 164, 214 (1927); 166, 1-15 (19271 (2) I A I R ~ %. (3) A l t s c t . A m u i , I : Phil. hIag, 171 7, 6iO-4 (1929). (4) l l x - c i . < ~ r n x mGitzz. : cliim. ital. 60,S33-42 (1930). ( 5 ) JYti.r.s: .J. Washington . h a d . Sci. 20, 1 4 6 4 (1930).
COhlXCSICXTION T O THE EDITOR A S O T E ON THE OXIDATIOS OF ACETOIS
Acetoin, acetylmethylcarbinol, exists a t ordinary temperatures in the liquid state and in a solid (polymerized) form (Pound and Wilson: J . Phys. Chem. 39, 1133 (1935)). It is known to oxidize to biacetyl. The solid polymer does not undergo oxidation in air or oxygen; one solid sample was kept for 227 days in oxygen (over mercury) without any diminlibion in the volume of the gas. The liquid acetoin, holvever, slowly and continually absorbed oxygen under these conditions. Three experiments were done, the liquid acetoin being initially spread out on filter paper a t the top of the eudiometer, but in time the liquid condensed over the tube and on top of the mercury. The room temperatures ThBLE 1
1
1 . .. . 2 . 3
iiam,
. . . 0.lDG .. 0.13 8O.llG - .~
I3incctyl . . , 0 . 2
~
'
