INORGANIC CHEMISTRY

S O L U B I L I T Y D I A G R A M OF T H E S Y S T E M L i A 1 H 4 - D I G L Y M E

A N D S O L U B I L I T Y I S O T H E R M IN T H E S Y S T E M

L i A 1 H 4 - K A 1 H ~ - D I G L Y M E AT 25 ~

U . M i r s a i d o v , S . I . B a k u m , a n d T . N . D y m o v a

UDC 541.8:541.123.2:546 .34'621'11:547.422

Diglyme, together with diethyl e ther and t e t r ahydro fu ran , is success fu l ly used as a medium for r e a c - t ions in which LiA1H 4 pa r t i c ipa t e s . Data on the solubil i ty of LiA1H 4 in diglyme at s eve r a l t e m p e r a t u r e s a re cited in [1]. This a r t i c l e p r e s en t s the r e su l t s of a study of the solubili ty of LiA1H 4 in diglyme in a broad range of t e m p e r a t u r e s , as well as the solubil i ty i so the rm in the s y s t e m LiA1H4-KA1H4-diglyme at 25 ~ The solubi l i ty in the t e r n a r y s y s t e m was studied to de te rmine the nature of the in teract ion in the case of d i s so lu- t ion of two a luminum hydr ides - those of l i thium and po ta s s ium - in diglyme.

EXPERIMENTAL METHOD

The interaction of the components was investigated by the methods of isothermal solubility, differential thermal (DrA) and visual-polythermal analyses, using the procedures and method of preparation of the solu- tions described earlier [2-4]. Crystalline LiAIH4, containing 98~ of the basic substance, was pro- duced according to the method of [4].

The content of aluminum in the liquid and solid phases was determined complexometrically withxylenol orange as the indicator [6]; lithium and potassium were determined by the method of flame photometry [7] on a PFM ~,~peetrophotometer. The composition of the solvates formed was calculated according to the data of DTA and a chemical analysis of the solid phases, existing at equilibrium at various temperatures.

D I S C U S S I O N O F R E S U L T S

L iAl t t4 -Dig lyme Sys tem. The resu l t s of an invest igat ion of the solubil i ty of LiAIH~ in diglyme a re p re sen ted in Fig. 1 and in Tab les 1-3. The liquidus line in the s y s t e m LiA1H4-diglyme consis ts of three b ranches . The f i r s t b ranch , on the por t ion 0-0.4 mole 70 LiAIH4, co r responds to the c rys ta l l i za t ion of pure diglyme (DG). The b ranch AB in the in terva l 0.4-4~ mole 70 co r re sponds to c rys ta l l i za t ion of the t r i so lva te LiA1H 4. 3DG, which mel t s incongruently at -8.5~ the b ranch BC cor re sponds to c rys ta l l i za t ion of the d i so lv- ate LiA1H 4, 2DG. The nonvariant point B at -8 .5 ~ and a concentra t ion of 4.0 mole 70 LiA1H 4 co r re sponds to the equi l ibr ium

LiA1H4.3DG~- ~ LiA1H4.2DG-~ DG

The r e su l t s of a chemical ana lys is of the solid phases , isolated under conditions close to i so the rmal , a r e cited in Tab le 2.

The densi ty of LiA1H 4. 2DG, found by the method of liquid pycnome t ry in toluene medium, is 1.03 g / c m 3. The r e su l t s of a de te rmina t ion of the solubil i ty of LiA1Ht in diglyme by the i so the rma l method (see Table 3) p rac t i ca l l y do not differ f r o m the data of the method of v i sua l -po ly the rma l ana lys i s .

LiA1Vt-KA1H 4- Diglyme Sys tem at 25 ~ The exper imenta l data on the solubil i ty in the t e r n a r y s y s t e m L i A 1 H t - K A l H t - d i g l y m e at 25 ~ a re cited in Table 4 and plotted graphica l ly in Gibbs coordinates in Fig. 2. The fo rma t ion of solid solutions and double sa l t s is not detected in the s y s t e m . The solubil i ty i so the rm cons is t s of ;wo b ranches , cor responding to c rys ta l l i za t ion of: the disolvate LiA1H 4. 2DG and unsolvated KA1H 4.

N. S, Kurnakov Insti tute of Genera l and Inorganic Chemis t ry , Academy of Sciences of the USSR. T r a n s l a t e d !From Izves t iya Akademii Nauk SSSR, Ser iya Khimicheskaya , No. 2, pp. 259-261, F e b r u a r y , 1973. Original a r t i c le submit ted March 13, 1972.

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251

T A B L E 1. Data of V i s u a l - P o l y t h e r - mal and Dif ferent ia l T h e r m a l A n a l y - s e s of the LiA1H 4- Dig lyme Sys t em

Content of LiA1H 4, in solution,%

T. of begin- I ingof crys- [ talliz~tion, I

Solid phase

0 0,17 0,30 0,7t 1,08 1,47 2,36 2,96 4,59 6,t2 7,00 8,69

--58,5 --5t ,0 --35,5 --2t --t0

0 t3,5 17,5 27 44 5t,5 65

DG LiA1H4.3 DG The same

LIA1Hr 2DG The same

n

N

H

T A B L E 2. Resul ts of Analys i s of Solid P h a s e s Isola ted f r o m Dig lyme Solutions of LiA1H 4

T. of iso- C, Ilation of

mole ~ crYScalS,

AI con- tent in precipi- tate, %

Mole ratio LiAiH4"di- glyme

2,48 3,72 9,79

t8,73

--25 --t2

i4,5 40

5,66 5,92 8,00 8,22

T A B L E 3. Solubil i ty of LiA1H 4 in Diglyme a c c o r d - ing to the Data of the I so - t h e r m a l Method. Solid P h a s e LiAIH �9 2DG

T ,~

t : 3,27 50 I : 3,12 50 t :2,23 70 t : 2 , t 6 70

Duration of experiment,

hours

Content of LiA1H 4 in

, solution, %

4 6 4 6

7,2t 7,t8 9,2t 9,05

%

.ig

0

-YL~

AJ x ~ ~ 6 ~ A L H ~ . Z , D G

DG-~aA~O~.~DO ~ I ~ lg Zg LiAI, H o. , mol 6/o

Fig . I

LLABH~

80Z/0/~~ 50

DG ~ ,~A~H~

F ig . 2

F ig . I. Fus ib i l i ty d i a g r a m of the L iA1Ha-d ig lyme sy s t e m: i) data of v i s u a l - p o l y t h e r m a l ana lys i s ; 2) data of d i f ferent ia l t h e r m a l ana lys i s ; 3) data of the method of i s o t h e r m a l solubi l i ty; 4) data of [1].

F i g . 2 . Solubil i ty i s o t h e r m in the s y s t e m L iA1H4-KA1H4-d ig lyme , 25 ~

T A B L E 4. g lyme Sys tem at 25 ~

Composition of liquid I Composition of preci- phase, % J pirate, ~

I LiA1H4 KA1H4 ] LiAIl t , KAIHa

4,t9 0 11,80 0 4,18 3,74 tt,25 0,73 3,99 5,99 8,55 1,68 4,03 8,44 t0,66 t ,60 4,0t 10,9 9,58 9,25 3,34 tl ,20 t ,7t 56,20 t ,89 13,00 0,33 78,89 t ,34 13,8t 0,32 71,20 0 14,56 0 7531

Solubil i ty in the LiA1H4-KA1H 4 - Di-

Solid phase

LiA1Ha.2 DG The same

u

Eutonic KA1H4 The same

n

The s y s t e m studied be longs to the s imp le eutonic type with eutonic compos i t i on c o r r e s p o n d i n g to 11.8 mole % LiA1H4, 17.4 mole % KA1H 4 and 70.8 mole % d ig lyme .

C O N C L U S I O N S

1. The l i q u i d - sol id equ i l ib r ium in the s y s t e m LiA1H 4- d ig lyme was s tudied in the t e m p e r a t u r e in - t e r v a l f r o m - 6 5 to 70 ~ and that in the s y s t e m LiA1H 4 - K A 1 H 4 - d i g l y m e at 25 ~

2. The ex is tence of the so lva tes LiA1H 4. 3DG and LiA1H 4. 2DG was es t ab l i shed .

3. LiA1H4, KA1H o and d ig lyme f o r m a s imp le eutonic s y s t e m ; the solubi l i ty i s o t h e r m at 25 ~ c o n s i s t s of the b r a n c h e s of c r y s t a l l i z a t i o n of LiA1H 4. 2DG and KA1H 4 with eutonic compos i t i on 11.8 mole % LiA1H4, 17.4 mole % KAIH4, and 70.8 mole % d ig lyme .

i. 2.

LITERATURE CITED

H. Clasen, Angew. Chemie, 73, 46 (1961). S. I. Bakum and T. N. Dymova---, Izv. Akad. Nauk SSSR, Ser. Khim., 1890 (1970).

252

So

4.

5.

6. 7.

T. 1~. Dymova, S. I. Bakum, So S. Grazhulene, and M. Mukhidinov, Izv~ Akad. Nauk SSSR, Ser. Khim., 1892 (1970). S. I~ Bakum, U. Mirsaidov, M. E. Kost, and T. N. Dymova, Izv. Akad. Nauk SSSR, Set. Khim., 2108 (1972) 0 G. A. Osipov, M. S. Belyaeva, G. K~ Klimenko, L. I. Zakharkin, and V. V. Gavrilenko, Kinetika i Kataiiz, 11, 901 (1970). R. Prshibil, Complexones in Chemical Analysis [Russian translation], IL (1960). N. S Poluektov, Methods of Analysis According to Flame Photometry [in Russian], Khimiya (1967).

253