Results and Discussion Table I gives the results of the analyscs pcrformed on the alkali fluoroplatinates. Only the cations were determined since the presence of the anion was confirmed by its characteristic absorption spectrum. TABLE I ANALYTICAL DAr.4
Cumpuutld n'd,~t17~
( NH4)gPtv6 KzPtFs RbgPtFtj CszPtFfl
y A l k a l 1 , %--Calcd Found
.
12 95 10.45 20.18 35.60 46.23
12.0 10.4 20.2 35.5 46.2
T h e solubilitics and dciisitics of tlic compounds at
25
f: 0.5'
are presented in Table 11. TABLE I1
Compound
Solubility, g./lOO ml. of s o h
Density
SazPtFd ZPtl'tj KzPtFs RbzPtFtj CSzPtFs
20,49 7.32 0.750 0.278 0.484
4.21 3.59 4.83 6.00 5.39
("4)
34S9
N UTES
July 5 , 1955
The solubility of the ammonium salt is to be noted and contrasted with the appreciably smaller solubilities of the ammonium and potassium chloroplatinates. Cox and Sharpe5 have mentioned the general tendency of the ammonium salts of fluoro complexes to be appreciably more soluble than the corresponding chloro complexes. This fact coupled with the smaller solubility of the potassium fluoroplatinate suggests that the gravimetric determination of potassium using fluoroplatinic acid as the precipitating reagent may be better than that with chloroplatinic acid. Schlesinger and Tapley2reported that very dilute solutions of potassium fluoroplatinate obeyed Beer's law. This was confirmed by measuring the 275 nip peak a t various concentrations of potassium, rubidium and cesium fluoroplatinates. These solutions, however, are relatively dilute even when saturated. Therefore] the more concentrated solutions of the sodium and ammonium salts were used for a further study. Llmmoniumfluoroplatinate solutions up to 0.05 ;M were measured and found to obey Beer's law within experimental error. However, the extinction coefficients of this salt differed slightly from those obtained for comparable concentrations of the potassium, rubidium and cesium salts. This may be attributed to the hydrolysis of the ammonium salt. The results of the study with the sodium salt reveal a small but definite departure from Beer's law. When the concentration was plotted against optical density, a slight curve was obtained which did riot pass through the oripin.
performed under the teriiis of a contract with thc AEC, Washington] D. C. DEPARTMENT OF CHEMISTRY THEGEORGE WASHlNGTON U N l V U R S I l Y WASHINGTON, D . C.
The System N ~ ~ S O ~ - L ~ Z S O ~at- H0"Z'O BY J. A . SKARULIS A A D H. A . HORAN RECEIVED JANUARY 20, 1055
'I'lic determination of the 0' isotherm of the system NazS04-LizS04-H20 was necessary in connection with a study of the system T\;azSOa-LizSO4.kl2(S04)~-HzO a t 0'. Although Spielrein2 reported, without presenting the supporting experimental data, a variety of double salts as stable solid phases (Na$304.LizS04,5.5Hz0a t 0 to 16'; 3NazS04.LizS04.12Hz0,16 to 24' ; Xa2sO4.4Li~SO4. 5Hz0,24 to 32'; Na2S04.LizS04.3Hz0,32 to loo'), the only double salts found in the recent study of two isotherms by Cavalca and Nardelli3 are 3NazS04-Li2S04-12H20 a t 27' and both 3NazSO4+ Li2SO4.12H20and NazS04.Li2S04a t 45.6'. The results presented here confirm the latter report in that the 0' isotherm is found to be similar, except for numerical relations, to that a t 27'. The sole solid phases are Na&04.10HzO, 3Nai304.LizS04. 12Hz0and LizS04.HzO. It is likely therefore that the only stable double salt solid phases of the system are those reported by Cavalca and Nardelli, who also described their crystallographic characteristics. Experimental Procedure T h e anhydrous simple salts were employed in the prepdration of mixtures of known composition. Li~S04.Hz0, a J . T. Baker reagent product, was dehydrated without fur; ther purification. I t was heated in pl2tinum at 550-600 after a preliminary dehydration a t 110 . Anhydrous NazSod, also a J . T. Baker reagent product, was similarly treated without the preliminary step. The sodium content of the dried Li2S04 was estimated by flame photometry and corrections applied in the calculation of the compositions of the mixtures. The apparatus and procedure was the same as t h a t described in a previous paper by the present authors4 dealing with another ternary system involving LizSOa. All complexes were seeded with a small crystal of iYa~S0~.10H?O. This was necessary to produce a solid phase in those mixtures which were relatively rich in NazSO4. Changes were also observed in most of the mixtures where a solid phase was already present. The complexes were mixed 24 hours before seeding and a t least 14 days before final analysis. Constancy of composition was used as a criterion of attainment of equilibrium. The filtered saturated solutions were analyzed for combined sulfates and for lithium, the sodium being obtained by difference. A given sample was evaporated to dryness a,t 100" and the residue heated to constant weight a t 180 . An ion-exchange chromatographic procedure,5,Gwith slight modifications, was then applied to the determination of the lithium in this residue. I n the procedure, both sodium and lithium were adsorbed on Colloidal Dowex 50 resin, the (1) This work was begun under a grant from t h e National Science Foundation. T h e major portion was completed with t h e assistance of a summer research grant fiom St. John's University to t h e principal author. (2) C. Spielrein, Compt. rend., 167, 46 (1913). (3) L. Cavalca and M. Nardelli, Gaze. chirn. ita$.,82,394 (1952). (4) J, A. Skarulis. H . A. Horan. et a!., THISJ O U R N A L , 76, 3096
3400
NOTES
lithium then eluted with 0.70 A4 HCl. The eluate was evaporated to LiCl and the lithium estimated by the Mohr titration of the chloride, after a small correction for free HC1 retained by the residue. The analytical procedure was tested with mixtures of kuoivn composition, the materials being the same as those used in the complexes. In these runs the sodium was also determined in the same manner as the lithium. The lithium values were reproducible with good precision but the sodium values obtained by direct measurement were in general unsatisfactory. Duplicate samples when passed through different columns yielded lithium values which seldom differed by more than 3 parts per 1000. The lithium values were consistently high by 5 i 1 parts per 1000. The sodium values on the other hand were 10 to 20 parts per 1000 high. I t was noted that the lithium values were not as good when the total number of equivalents in the saniple was low. For this reason, the weights of saturated solutions taken for analysis were such t h a t the aliquots introduced into the columns contained a t least I me. of lithium. All analyses were run in duplicate on separate samples of saturated solution. The results are tabulated in Table I aiid plotted in the usual manner in Fig. 1 .
Hin i n ' )
/
~~ ~~
SazSO4 ( A ) Fig. 1.-The
LizSOa ( B j system Na2SO,-LigSO,-H*O at 0".
VOl. 77 TABLE I THESYWEM Xa?SO~-LiaSO4-ll29 A T 0" A = SaaSOa, B = Li?SOa,\I: = €I&. A,
1 2 3
1 5 ii
7 8 0 10 11 12 1:3 11 1,; 16 17 IS 19
Complex 'Z B,
76
13.01 16.06
2.46 6.48 1.5.08 9 . 9 9 10.07 13.9'7 9.57 17.97 9 . 0 5 21.91 14.95 20.90 19.84 20.96 18.01 21.3:: 18.00 21.56 21.43 20.96 18 35 2,?.88 18.00 2t?.0;3 16.91 3 k 4 5 18.26 2!).6') ll.O(i 2 8 . 8 6 9.2.i 3 2 . 2 1 5.05 X . 8 i i 2 . 1 0 34.8ii
Solution
A,
70
4.40 4.83 4.95 5.25 5.73 6.22 6.30 6.17 6.23 6.10 6.04 5.87 5.81 5.87 5.84 5.83 5.57 5.99 2.36
B, ';b
3.17
9.09 13.58 16.01 20.02 23.31 23.23 23.41 23.37 23.72 23.80 24.12 24.16 24.15 21.14 2-1.14 21.12 24.03 25.52
+ +
+ +
-+ +
B.\\' B ,\V
the tie-lines of complexes 1-3 inclusive to 70 Li2SOd a t 44.09% Na2S04,the theoretical % NaS04 in the decahydrate, gives values of -0.10, -0.03, -0.29, -0.43 and -0.46, respectively. The tie-lines of complexes 8-1 1 inclusive when extrapolated to % Li2S04 a t 56.65% xa2S04, the theoretical % Nazso4 in the double salt, yield the values 14.36, 14.64, 14.54 and 14.56,respectively, as compared to a theoretical value of 14.61. The solid phases of these four complexes were centrifuged and analyzed for water content. The nearly free-flowitig crystalline material contained 30y0 HzO as compared with the theoretical value 28.74. Extrapolation of coin:ilexes 18-19 to yo Na2S04 a t 83.93% Li2sO4, the theoretical % LiZSO4 in the monohydrate, gives values of +0.07 and 1-0.68, respectively. In general, the above extrapolations deviate in the direction expected because the lithium analyses of the saturated solutions are slightly high, as indicated in a preceding paragraph. KO attempt was made to correct these analyses.
Discussion of Results Xlgebraic extrapolation7 of the data indicates three solid phases a t 0' : Na.804.10H20, 3Na2SO4. DEPARTMENT OF CHEMISTRY Li2S04.12Hz0 and Li&04.Hz0. Extrapolation of ST. JOHN'S I,*SIVERSITY ( 7 ) A. E . Hill and J . I , Ricci, THISJ O U R N A I . , 63, 4306 (1931).
SCI I L < l
-4,10\\' A , lo\\. A . 1(ILLA . lO\\' A . 1O\V A,lO\V 3A,13,12\V A,10\V 3A,H.I2\i' 3A .B, 12\\. 3A.B.12\\. 3A. R ,12\i. 3A.B.12\\. 3A,R,12\\. I
