Gallium, Indium, Thallium

S E C T I ON 16

Gallium, Indium, Thallium

E. DONGE S

Galliu m Ga

In t h e m e t h o d of Sebba a n d P u g h , t h e e l e c t r o l y s i s v e s s e l i s a 2 5 0 - m l . b e a k e r . T h e i n s i d e w a l l of t h e b e a k e r i s l i n e d w i t h a p i e c e of P t foil 20 c m . long and 3 c m . w i d e . T h i s s e r v e s a s t h e a n o d e . T h e c a t h o d e c o n s i s t s of a t h i c k s h e e t of P t , 1.5 c m . w i d e a n d 3 c m . l o n g . Its l o w e r e d g e i s w e d g e s h a p e d a n d i s s e a l e d into t h e l o w e r end of a g l a s s U t u b e ( F i g . 247a). T h i s s e a l point i s e n l a r g e d to a c u p l i k e s h a p e . T h e c a t h o d e i s s e a l e d into t h e U t u b e in s u c h a f a s h i o n t h a t t h e c o n n e c t i o n t o t h e c o n d u c t i n g P t w i r e i s j u s t i n s i d e t h e g l a s s - m e t a l s e a l . (If t h e w i r e w e r e t o e x t e n d b e y o n d t h i s s e a l , it would r a p i d l y c o r r o d e a t t h e point w h e r e it c o m e s in c o n t a c t w i t h t h e s o l u t i o n . If t h e a p p a r a t u s i s a r r a n g e d a s i n d i c a t e d , no c o r r o s i o n c a n b e o b s e r v e d e v e n a f t e r s e v e r a l h u n d r e d h o u r s of o p e r a t i o n . ) T h e o t h e r end of t h e P t w i r e d i p s into a Hg pool w h i c h , in t u r n , i s c o n n e c t e d t o t h e p o w e r s u p p l y by a n o t h e r l e a d w i r e .

T h e " c u p " f o r m e d a t t h e e l e c t r o d e end of t h e U t u b e i s 3 c m . in d i a m e t e r and v e r y s h a l l o w ; n e v e r t h e l e s s , it c a n hold m o r e t h a n 10 g. of m o l t e n G a . A s a r e s u l t of t h e h e a t p r o d u c e d by t h e h i g h r e s i s t a n c e of t h e c e l l , t h e G a s e p a r a t e s a s t h e liquid. B e c a u s e t h e Ga i s in c o n t a c t w i t h t h e c a t h o d e d u r i n g o p e r a t i o n , it i s a l s o c a t h o d i c H e n c e it c a n b e r e a d i l y w a s h e d , d r i e d a n d w e i g h e d d i r e c t l y in t h e c u p . T h i s a r r a n g e m e n t t h e r e f o r e p e r m i t s q u a n t i t a - t i v e w o r k .

B e f o r e l o a d i n g t h e c e l l t h e Ga i s f i r s t p r e c i p i t a t e d a s t h e h y d r o x i d e , u s i n g no m o r e t h a n t h e e q u i v a l e n t of 10 g. of t h e m e t a l . It i s t h e n d i s s o l v e d in t h e m i n i m u m v o l u m e of c o n c e n t r a t e d NaOH a n d d i l u t e d with H²0 t o 150 m l . W i t h a c u r r e n t of 1 a m p . ( 3 - 4 v . ) , 6 g. (of t h e 10) i s o b t a i n e d d u r i n g t h e f i r s t 24 h o u r s ; in t h e n e x t 24 h o u r s 3.5 g. m o r e s e p a r a t e s . T h e r e m a i n i n g 0.5 g. s e p a r a t e s s o s l o w l y , h o w e v e r , that it i s e x p e d i e n t to p r e c i p i t a t e it with s o d i u m h y d r o x i d e and t o u s e it in t h e n e x t e l e c t r o l y s i s .

8 3 7

838 Ε . D O N G E S

B r a u e r w a s a l s o a b l e to o b t a i n good r e s u l t s with a s i m p l e r c a t h o d e a r r a n g e m e n t , shown in F i g . 247 b , when t h e a m o u n t of Ga to b e s e p a r a t e d e x c e e d s 10 g. In s o m e c a s e s a l u m i n u m i s an i m p u r i t y a n d b e c o m e s a p p r e c i a b l y c o n c e n ­ t r a t e d in t h a t p o r t i o n of t h e Ga w h i c h h a s not b e e n s e p a r a t e d by e l e c t r o l y s i s . T h e two a r e s e p a ­ r a t e d by p r e c i p i t a t i o n w i t h c u p - f e r r o n ; t h e p r e c i p i t a t e i s a s h e d and c o n v e r t e d to t h e h y d r o x i d e by fusion w i t h NaOH.

R e s i d u a l Ga s t i l l a d h e r i n g to t h e c a t h o d e i s r e m o v e d by r i n s i n g down with w a r m , d i l u t e h y d r o c h l o r i c a c i d . T h e Ga i m m e d i a t e l y f o r m s tiny s p h e r e s , w h i c h a r e r e a d i l y w i p e d off.

T h e s e p a r a t e d Ga c o n t a i n s t r a c e s of P t . T h e s e c a n b e r e m o v e d , a l o n g w i t h any t r a c e s of P b and Sn w h i c h m a y b e p r e s e n t , by t h e following m e t h o d : Ga i s m e l t e d u n d e r a l a y e r of w a t e r a n d a n e q u a l v o l u m e of c o n c e n t r a t e d h y d r o c h l o r i c a c i d a d d e d . After t h e m e t a l h a s b e e n s w i r l e d five m i n u t e s u n d e r n e a t h t h e a c i d , t h e l a t t e r i s c a r e f u l l y w a s h e d out and s o m e c o n c e n t r a t e d n i t r i c a c i d i s a d d e d . T h e r e a c t i o n i s v i g o r o u s at f i r s t and t h e m e t a l i s c o n v e r t e d to tiny s p h e r e s . T h e a c i d i s d i l u t e d w i t h w a t e r a f t e r a few m i n u t e s and c a r e f u l l y w a s h e d out a f t e r a n o t h e r 10 m i n u t e s . T h e Ga a c q u i r e s i t s m e t a l l i c l u s t e r a g a i n on r e n e w e d w a s h i n g w i t h d i l u t e h y d r o c h l o r i c a c i d ( p r o b a b l y b e c a u s e of d e ­ s t r u c t i o n of a s u r f a c e oxide f i l m ) , and t h e tiny s p h e r e s c o a l e s c e .

About 5% of t h e Ga d i s s o l v e s d u r i n g p u r i f i c a t i o n . Although a m i x t u r e of h y d r o c h l o r i c and n i t r i c a c i d s (aqua r e g i a ) i s not u s e d , t h e Ga i s s p e c t r o s c o p i c a l l y f r e e of P t (and a l s o of P b and Sn) a f t e r t h e t r e a t m e n t .

G a l l i u m c a n a l s o b e r e c o v e r e d f r o m w e a k l y a c i d i c s o l u t i o n s v i a t h e m e t h o d s u g g e s t e d by t h e E l e c t r o n i c s S e r v i c e s R e s e a r c h L a b o r a t o r y . T h u s , G a C l³ i s d i s s o l v e d in d i s t i l l e d w a t e r and e l e c t r o l y z e d in a q u a r t z v e s s e l b e t w e e n a P t a n o d e a n d a T a c a t h o d e . T h e g a l l i u m s e p a r a t e s at t h e c a t h o d e a n d s i n k s to t h e b o t t o m of t h e v e s s e l . It i s s e p a r a t e d , w a s h e d , a n d d r i e d .

PROPERTIES:

A t o m i c w e i g h t 6 9 . 7 2 . L e a d - g r a y m e t a l w i t h b l u i s h l u s t e r . T h e m e l t h a s a s i l v e r y - w h i t e l u s t e r a n d a m a r k e d t e n d e n c y to s u p e r c o o l , F i g . 2 4 7 . C a t h o d e s for e l e c ­

t r o l y t i c s e p a r a t i o n of g a l ­ l i u m , a) a c c o r d i n g to Sebba and Pugh; b) s i m p l e a r ­ r a n g e m e n t , w h i c h h a s b e e n u s e d s u c c e s s f u l l y in t h e U n i v e r s i t y of F r e i b u r g

L a b o r a t o r y .

1 6 . G A L L I U M , I N D I U M , T H A L L I U M 839 but s o l i d i f i e s on s e e d i n g w i t h s o l i d Ga o r a p i e c e of Dry I c e . Stable in a i r . M . p . 29.78°C, b . p . 2064°C; d 5.90; d (liq., 30°C) 6.09. C r y s t a l t y p e A 1 1 . H a r d n e s s 1.5.

REFERENCES:

F . Sebba and W. Pugh, J. C h e m . Soc. (London) 1937, 1 3 7 3 . L. M o s e r a n d A. B r u k l , M o n a t s h . C h e m . 5 1 , 325 (1929).

G. B r a u e r , p r i v a t e c o m m u n i c a t i o n (1950).

C h e m . E n g . N e w s 34, 2887 (1956).

DISSOLVING OF METALLIC GALLIUM IN ACIDS

G a l l i u m i s only s l i g h t l y m o r e n o b l e t h a n Zn. H o w e v e r , it d i s - s o l v e s in m i n e r a l a c i d s slowly due to s u r f a c e p a s s i v i t y p h e n o m e n a . Hot, c o n c e n t r a t e d n i t r i c a c i d i s t h e m o s t effective, d i s s o l v i n g 5 g.

of Ga in 10 h o u r s . Sebba and P u g h r e p o r t a c h i e v i n g r a p i d s o l u t i o n of Ga in c o n c e n t r a t e d n i t r i c a c i d if t h e m e t a l , w h i c h d i s p e r s e s in tiny s p h e r e s d u e to t h e a c t i o n of hot a c i d , i s a l t e r n a t e l y c o o l e d t o a p o w d e r y a c i d - m e t a l m i x t u r e a n d t h e n r e h e a t e d .

GALLIUM (III) PERCHLORATE Ga (C10⁴)³ · 6 H^aO

F o s t e r c l a i m s that c o n c e n t r a t e d p e r c h l o r i c a c i d ( e s p e c i a l l y w h e n m i x e d w i t h c o n c e n t r a t e d s u l f u r i c acid) d i s s o l v e s Ga s i g n i f i - c a n t l y m o r e r a p i d l y t h a n c o n c e n t r a t e d n i t r i c a c i d : 5 g. of Ga, h e a t e d in 60 m l . of 72% H C 1 0⁴, d i s s o l v e s within an h o u r .

T h e r e s u l t i n g G a ( C 1 0⁴)³ · 6 H²0 s e p a r a t e s a l m o s t c o m p l e t e l y on c o o l i n g and in s u c h l a r g e c r y s t a l s t h a t it c a n r e a d i l y b e i s o l a t e d on a f r i t t e d g l a s s f i l t e r . T h e d a m p c r y s t a l s s h o u l d not c o m e in c o n t a c t with o r g a n i c m a t e r i a l s ( e . g . , f i l t e r p a p e r ) s i n c e t h e c o n - c e n t r a t i o n of t h e a d h e r i n g p e r c h l o r i c a c i d i s g r e a t e r t h a n 72%

due to t h e l o s s of w a t e r in t h e f o r m of t h e h e x a h y d r a t e . T h e c r y s t a l s a r e v a c u u m - d r i e d f o r one h o u r at 125°C.

PROPERTIES:

F o r m u l a w e i g h t 4 7 6 . 1 9 . V e r y r e a d i l y s o l u b l e in w a t e r and a l c o h o l ; d e l i q u e s c e s in t h e a i r . D e c o m p o s i t i o n b e g i n s at 175°C at a t m o s p h e r i c p r e s s u r e a n d at 155° C in v a c u u m . C r y s t a l l i z e s slowly a s l a r g e o c t a h e d r a .

REFERENCES:

F . Sebba and W. P u g h , J . C h e m . Soc. (London) 1937, 1 3 7 3 . L. S. F o s t e r , J. A m e r . C h e m . Soc. 6 1 , 3122 (1933).

8 4 0 Ε . D O N G E S

TrimethylgaIlium , Tetramethyldigallane , Digallan e

Ga(CH³)³, Ga²H²(CH³)⁴, Ga²H⁶

W i b e r g a n d J o h a n n s e n s t a t e t h a t Gas Hs i s f o r m e d by t h e r e a c t i o n of t r i e t h y l a m i n e and t e t r a m e t h y l d i g a l l a n e ; t h e l a t t e r i s f o r m e d by e l e c t r i c a l glow d i s c h a r g e in a m i x t u r e of H² and g a l l i u m t r i m e t h y l .

T h e w o r k w a s c a r r i e d out in a Stock h i g h - v a c u u m a p p a r a t u s ( s e e P a r t I, p . 66) b e c a u s e of t h e s e n s i t i v i t y of t h e s e c o m p o u n d s to a i r , m o i s t u r e , and s t o p c o c k g r e a s e . T h e a p p a r a t u s w a s c o n ­ s t r u c t e d a c c o r d i n g to W i b e r g and S i i t t e r l i n ' s d i r e c t i o n s ; h o w e v e r , e a c h t r a p w a s a l s o c o n n e c t e d to t h e l a r g e d i a m e t e r p u m p manifold v i a a Stock v a l v e s o t h a t an o p t i m u m v a c u u m c o u l d b e m a i n t a i n e d by t h e p u m p d u r i n g t h e t r a n s p o r t of m a t e r i a l .

The f r a c t i o n a t i o n w a s c a r r i e d out in a C l u s i u s and R i c c o b o n i a p p a r a t u s ( s e e a l s o P a r t I, p . 7 0 ) , w h i c h w a s i n c o r p o r a t e d in t h e h i g h - v a c u u m s y s t e m ; t h i s a p p a r a t u s h a s b e e n s i m p l i f i e d by C l u s i u s s o t h a t t h e v a p o r s t r e a m flows t h r o u g h an a d j u s t a b l e c e r a m i c c o n e v a l v e into t h e c o n d e n s a t i o n t r a p .

A) TRIMETHYL GALLIUM

2Ga + 3Hg(CH³)² = 2Ga(CH³)³ + 3 H g

139.4 692.0 229.6 601.8

In t h e m e t h o d of W i b e r g , J o h a n n s e n and S t e c h e r , i m p r o v e d by C o a t e s , 6.75 g. of m e t a l l i c Ga and 37 g. of H g ( C H³)² a r e h e a t e d to boiling at a t m o s p h e r i c p r e s s u r e in t h e p r e s e n c e of a t r a c e of HgClg. A f l a s k with a f u s e d - o n 2 0 - c m . f r a c t i o n a t i n g c o l u m n i s u s e d and d r y n i t r o g e n i s p a s s e d t h r o u g h . T h e c o l u m n h e a d t e m ­ p e r a t u r e b e g i n s to d r o p b e l o w 92°C [b.p. of H g ( C H³)²] a f t e r two h o u r s and r e m a i n s at 55-56°C [b.p. of G a ( C H³)³] a f t e r five h o u r s . S m a l l q u a n t i t i e s of p u r e G a ( C H³)³ a r e w i t h d r a w n f r o m t i m e to t i m e at t h e c o l u m n h e a d o v e r a t h r e e - d a y p e r i o d , u n t i l a r e s i d u e of about 1 m l . [chiefly G a ( C H³)³] r e m a i n s a l o n g w i t h t h e Hg f o r m e d . C o n v e r s i o n p r o c e e d s a l m o s t q u a n t i t a t i v e l y and without d e c o m p o s i ­ tion.

T h e G a ( C H³)³ d i s t i l l a t e i s f r o z e n and t r a n s f e r r e d u n d e r n i t r o ­ gen to a v a c u u m a p p a r a t u s w h e r e it c a n b e k e p t u n d e r i t s own v a p o r p r e s s u r e until f u r t h e r u s e .

PROPERTIES:

F o r m u l a w e i g h t 1 1 4 . 8 2 . M.p. —15.8°C, b . p . (762 m m . ) 5 5 . 7 ; v a p o r p r e s s u r e (0°C) 64.5 m m . V e r y s e n s i t i v e to oxygen.

B) TETRAMETHYL DIGALLANE

2Ga(CH³)³ + n H² = Ga²H²(CH³)⁴ + 2CH⁴ (C²H⁶)

229,6 201.6

T h e p r i n c i p l e of t h e e x p e r i m e n t a l e l e c t r o l y t e - H² c e l l w a s d e v e l o p e d by Stock and S u t t e r l i n and f u r t h e r i m p r o v e d by W i b e r g and J o h a n n s e n and W i b e r g and S t e c h e r . The s y s t e m i s s a t u r a t e d w i t h G a ( C H³)³ at 760 m m . a n d —44°C [the H² : G a ( C H³>³ r a t i o i s t h e n 200 : l ] , p l a c e d in a n i c e - c o o l e d c e l l , and s u b j e c t e d t o a 3 . 4 - m a . glow d i s c h a r g e at a c e l l p r e s s u r e of 12.2 m m . T h e h y d r o g e n i s f r e e d of Qs t r a c e s by p a s s a g e o v e r p l a t i n i z e d a s b e s t o s a t 300°C and t h e r e s u l t i n g m o i s t u r e r e m o v e d by f r e e z i n g out.

T h e G a²H²( C H³)⁴ f o r m e d i s f r o z e n out of t h e H² s t r e a m at liquid n i t r o g e n t e m p e r a t u r e . It i s f r e e d of u n r e a c t e d G a ( C H³)³ ( c o n d e n s i n g a t —80°C) and b y p r o d u c t h y d r o c a r b o n s ( c o n d e n s i n g at —196°C) by f r a c t i o n a t i o n at r o o m t e m p e r a t u r e a n d c o n d e n s a t i o n at - 3 0 ° C .

T h e y i e l d i s 6 0 - 7 0 % .

PROPERTIES:

C o l o r l e s s , highly v i s c o u s , r e l a t i v e l y n o n v o l a t i l e liquid; s o l i d i - f i e s to a g l a s s and s o f t e n s without any w e l l - d e f i n e d m . p . D e c o m - p o s e s a b o v e 130°C into G a ( C H³)³, Ga a n d Hq. C a l c u l a t e d b . p . 172°C. V a p o r p r e s s u r e (0°C) 0.5 m m . ; ( 2 0 ° C ) 2 m m . ; (95°C) 64 m m . V e r y s e n s i t i v e to O g, m o i s t u r e a n d s t o p c o c k g r e a s e .

C) DIGALLANE

3Ga²H²(CH³)⁴ + 4 N ( C²H⁵)³ = 4Ga(CH³)^s · N(C²H⁵)³ + Ga²H⁶

604.8 404.8 864.0 145.5

In t h e m e t h o d of W i b e r g and J o h a n n s e n , 2 3 5 . 1 m g . of t e t r a - m e t h y l d i g a l l a n e a n d 157.5 m g . of t r i e t h y l a m i n e , w h i c h h a s b e e n c o m p l e t e l y d r i e d o v e r p i e c e s of Na and t h e n f r a c t i o n a t e d , a r e c o n d e n s e d (3 : 4 m o l e r a t i o ) in a c o l d t r a p . T h e t r a p i s s e a l e d a n d t h e c o n t e n t s a r e a l l o w e d to t h a w . G e n t l e h e a t i n g r e s u l t s in c o n - v e r s i o n to a t r i m e t h y l g a l l i u m - t r i e t h y l a m i n e a d d u c t a n d d i g a l l a n e . T h e r e a c t i o n p r o d u c t s a r e s e p a r a t e d by f r a c t i o n a t i o n at r o o m t e m p e r a t u r e , in w h i c h G a ( C H³)³ · N ( C²H s )³ ( v a p o r p r e s s u r e 0.04 m m . a t 0°C, m . p . 96°C, b . p . 167°C) i s c o n d e n s e d at —10°C and GasHe at - 1 9 6 ° C .

T h e y i e l d i s 5 6 . 5 m g . ( t h e o r e t i c a l : 56.8 m g . ) .

PROPERTIES:

C o l o r l e s s , v e r y m o b i l e liquid. M . p . —21.4°C, v a p o r p r e s s u r e (0°C) 2.5 m m . ; (54°C) 4 9 . 1 m m . C a l c . b . p . 139°C, b u t b e g i n s t o d e c o m p o s e at 130°C t o Ga a n d H².

8 4 2 Ε . D O N G E S R E F E R E N C E S:

Lithium Tetrahydrogallat e

GaCl³ + 4 LiH = 3 LiCl + LiGaH⁴

176.1 31.8 127.2 80.7

Finholt, Bond and S c h l e s i n g e r r e p o r t t h a t L i G a H⁴ c a n b e p r e ­ p a r e d in t h e s a m e m a n n e r a s L i A l H⁴ ( s e e p . 805). A g r o u n d joint flask with a c u r v e d t u b e fused on i s u s e d . T h e f l a s k i s c h a r g e d w i t h 470 m g . of LiH (fourfold e x c e s s ) a n d i s c o n n e c t e d t o a Stock h i g h - v a c u u m s y s t e m by m e a n s of a b a l l joint, w h i c h p e r m i t s t h e flask to b e m o v e d . T h e n 599 m g . of a n h y d r o u s G a C l³ i s s u b l i m e d into t h e r e a c t i o n f l a s k and about 5 m l . of d r y e t h e r c o n d e n s e d on t o p of it by c o o l i n g t h e f l a s k in liquid n i t r o g e n . T h e e t h e r i s slowly h e a t e d u n t i l t h e G a C l³ d i s s o l v e s in it. Then t h e c o n t e n t s a r e c o o l e d to —80°C.

L i t h i u m h y d r i d e i s t h e n a d d e d slowly t o t h e e t h e r f r o m t h e s i d e a r m by c a r e f u l l y t u r n i n g t h e b a l l j o i n t . After t h e i n i t i a l v i g o r o u s r e a c t i o n h a s s u b s i d e d , t h e flask i s a l l o w e d to w a r m g r a d u a l l y t o r o o m t e m p e r a t u r e . W i b e r g and S c h m i d t r e p o r t a q u a n t i t a t i v e y i e l d if t h e e t h e r s o l u t i o n i s r e f l u x e d for 1.5 h o u r s on a w a t e r b a t h (35°C) a f t e r t h e e x o t h e r m i c r e a c t i o n s t a g e i s o v e r . The e t h e r s o l u t i o n of L i G a i ^ i s finally f o r c e d t h r o u g h a g l a s s f r i t with d r y , C O g - f r e e N² and s e p a r a t e d f r o m e x c e s s LiH and p r e ­ c i p i t a t e d L i C l . V a c u u m d i s t i l l a t i o n of t h e e t h e r at r o o m t e m p e r a ­ t u r e l e a v e s a w h i t e r e s i d u e of L i G a H⁴.

T h e final p r o d u c t i s a n a l y z e d by h y d r o l y s i s a n d m e a s u r i n g t h e l i b e r a t e d H²; Ga i s d e t e r m i n e d a s t h e h y d r o x y q u i n o l a t e . T h e

Ε . W i b e r g and Τ . J o h a n n s e n , Die C h e m i e 55^ 38 (1942).

T . J o h a n n s e n , T h e s i s , Munich, 1 9 4 1 .

G. E. C o a t e s , J . C h e m . S o c (London) 1 9 5 1 , 2 0 1 1 .

A. Stock, B e r . d t s c h . c h e m . G e s . A 54, 142 (1921); s e e a l s o P a r t I, t h i s book, p . 66.

E . W i b e r g and W. S u t t e r l i n , Z. a n o r g . a l l g . C h e m . 202, 1 (1931).

K. C l u s i u s and L. R i c c o b o n i , Z. p h y s . C h e m . (B) 3 8 , 81 (1938).

A. Stock, Z. E l e k t r o c h e m . 39, 256 (1933).

E. W i b e r g , T . J o h a n n s e n and O . S t e c h e r , Z. a n o r g . a l l g . C h e m . 2 5 1 , 114 (1943).

E. W i b e r g and O . S t e c h e r , p r i v a t e c o m m u n i c a t i o n .

A. Stock and W. S u t t e r l i n , B e r . d t s c h . c h e m . G e s . 6 7 , 407 (1934);

s e e a l s o E. W i b e r g and M. S c h m i d t , Z. N a t u r f o r s c h . 7 b , 577 (1952).

8 4 3 y i e l d i s 76%, t h e p u r i t y 93%. T h e y i e l d d e p e n d s chiefly on t h e e x t e n t t o w h i c h t h e L i C l i s w a s h e d out, a n d t h e p u r i t y on t h e e x t e n t t o w h i c h t h e e t h e r i s r e m o v e d .

H e a t i n g d e c o m p o s e s L i G a H⁴ to Ga and p r o b a b l y LiH and H².

REFERENCES:

A. E . F i n h o l t , A. C. Bond, J r . and H. J. S c h l e s i n g e r , J . A m e r . C h e m . Soc. 69, 1199 (1947); s e e a l s o E . W i b e r g a n d M. S c h m i d t , Z. N a t u r f o r s c h . 6_b, 171 (1951); 7_b_, 576 (1952).

Gallium(lll ) Chlorid e

I. G a203 + 3 SOCl2 = 2 G a C l3 + 3 S 02

187.4 356.9 352.2 192.2

A m i x t u r e of 2.5 g. of i g n i t e d G a²0³ a n d about 8 m l . of S O C l² ( t w o - to t h r e e f o l d e x c e s s ) i s h e a t e d s e v e r a l h o u r s at 200°C in a s e a l e d t u b e , a c c o r d i n g t o H e c h t , J a n d e r and S c h l a p m a n n . C o m - p l e t e c h l o r i n a t i o n of t h e G a²0³ o c c u r s . T h e t u b e i s p r e c o o l e d t o

—10°C b e f o r e opening, t o r e d u c e t h e p o s i t i v e p r e s s u r e g e n e r a t e d by t h e S 0² f o r m e d . T h e S 0² i s a l l o w e d t o e v a p o r a t e at r o o m t e m p e r a t u r e , e x c e s s SOCI2 i s d i s t i l l e d off ( b . p . 75.7°C), and G a C l³ i s d i s t i l l e d at 220°C.

F i s c h e r and J u b e r m a n n s t a t e t h a t G a C l³ c a n b e o b t a i n e d c o m - p l e t e l y p u r e by v a c u u m s u b l i m a t i o n in q u a r t z e q u i p m e n t .

II. K l e m m and Tilk o b t a i n e d G a C l³ by h e a t i n g G a²0³ in a s t r e a m of C l² and C C 1⁴; C l² a l o n e did not r e a c t a p p r e c i a b l y w i t h G a²0³ u p to 800°C.

III. Ga + 1 V2C 12 = G a C l3

69.7 106.4 176.1

R i c h a r d s , C r a i g and S a m e s h i m a r e p o r t f o r m a t i o n of G a C l³ by b u r n i n g m e t a l l i c Ga in a s t r e a m of C l^s. S p e c t r o s c o p i c a l l y p u r e G a C l³ m a y b e o b t a i n e d by r e p e a t e d f r a c t i o n a l e v a p o r a t i o n in a s t r e a m of C l² and N² and finally in v a c u u m .

T h e following m e t h o d s w a s d e v e l o p e d by t h e E l e c t r o n i c S e r v - i c e s R e s e a r c h L a b o r a t o r y f o r p r e p a r a t i o n of s p e c t r o s c o p i c a l l y p u r e G a C l³. C h l o r i n e , m i x e d w i t h N³ c a r r i e r g a s , i s b u b b l e d t h r o u g h m o l t e n c o m m e r c i a l G a . T h e r e s u l t a n t G a C l³ i s d i s t i l l e d into a P y r e x t u b e ( e . g . , 25 c m . long, 2.5 c m . in d i a m e t e r ) u n d e r a N² p r o t e c t i v e a t m o s p h e r e . T h e t u b e i s s e a l e d w h e n half full and t h e G a C l³ s u b j e c t e d t o z o n e m e l t i n g . If t h e s t a r t i n g Ga

8 4 4 Ε. DONGES

c o n t a i n s 10-70 m g . / k g . of i m p u r i t i e s , a f t e r 20 p a s s e s a l l i m p u r i t i e s a r e c o n c e n t r a t e d in one q u a r t e r of t h e p r e p a r a t i o n . T h e r e s t ( t h r e e q u a r t e r s ) of t h e ingot s o t r e a t e d c o n s i s t s of a c l e a r , c r y s ­ t a l l i n e m a s s , in w h i c h no i m p u r i t i e s c a n b e d e t e c t e d by s p e c t r o ­ s c o p i c m e t h o d s . T h e o t h e r q u a r t e r , c o n t a i n i n g t h e i m p u r i t i e s , i s u n m i s t a k a b l e b e c a u s e of i t s c o l o r and m a y r e a d i l y b e c u t off. T h e Ga c o n t a i n e d in it i s r e c o v e r e d by e l e c t r o l y s i s ( s e e p . 837).

IV. Heyne c l a i m s G a C l³ i s b e s t p r e p a r e d by h e a t i n g m e t a l l i c Ga at 200-400°C in a s t r e a m of d r y HC1 followed by d i s t i l l a t i o n .

PROPERTIES:

C o l o r l e s s , n e e d l e - s h a p e d , v e r y h y g r o s c o p i c c r y s t a l s ; f u m e s and d e l i q u e s c e s in a i r . M . p . 77.9°C, b . p . 201.3°C; d 2 . 4 7 . D i s ­ s o l v e s in w a t e r , evolving l a r g e q u a n t i t i e s of h e a t . V e r y r e a d i l y s o l u b l e in e t h e r ; s h a k i n g a 5.5N HC1 (optimum) G a C l³ s o l u t i o n w i t h t h e s a m e v o l u m e of e t h e r ( r e p e a t e d l y p r e e x t r a c t e d with 5.5N HC1) e x t r a c t s 98% of t h e G a C l³ ( p a r t i t i o n coefficient = 7 5 ; s e e F i g . 248) [Ε. H. Swift, J . A m e r . C h e m . S o c 4 6 , 2375 (1924)].

Starting solution, m o l e s of Η CI/ liter

F i g . 2 4 8 . P a r t i t i o n of Ga(III) c h l o r i d e b e t w e e n e t h e r and a q u e o u s p h a s e a s a function of t h e HC1 c o n c e n t r a t i o n in t h e

s t a r t i n g s o l u t i o n .

W. F i s c h e r and S. L a u t e r [ G e r m a n P a t e n t 801,986 (1949)] c l a i m that o t h e r e t h e r s , s u c h a s d i i s o p r o p y l and d i i s o b u t y l , a r e b e t t e r s u i t e d t h a n d i e t h y l e t h e r f o r t h e s e l e c t i v e e x t r a c t i o n f r o m a q u e o u s h y d r o c h l o r i c a c i d , d u e t o t h e i r l o w e r w a t e r s o l u b i l i t y . A l s o , t h e i r l o s s e s would s e e m t o b e s u b s t a n t i a l l y l o w e r b e c a u s e of t h e i r l o w e r s o l u b i l i t y , e s p e c i a l l y in r e c y c l e o p e r a t i o n s . F i s c h e r and L a u t e r

1 6 . G A L L I U M , I N D I U M , T H A L L I U M 845 f u r t h e r d e m o n s t r a t e d t h a t o p t i m u m c o n d i t i o n s for t h e a q u e o u s p h a s e d e p e n d chiefly on t h e c h l o r i d e ion c o n c e n t r a t i o n , r a t h e r t h a n on t h e HC1 c o n c e n t r a t i o n , and t h a t t h e r e f o r e a c o n s i d e r a b l e p o r t i o n of t h e HC1 m a y b e r e p l a c e d by an e q u i v a l e n t q u a n t i t y of r e a d i l y s o l u b l e m e t a l c h l o r i d e .

REFERENCES:

I. H. H e c h t , G. J a n d e r and H. S c h l a p m a n n , Z. a n o r g . a l l g . C h e m . 254, 255 (1947).

W. F i s c h e r and O. J i i b e r m a n n , Z. a n o r g . a l l g . C h e m . 227, 227 (1936).

II. W. K l e m m and W. Tilk, Z . a n o r g . a l l g . C h e m . 2 0 7 , 161 (1932).

III. T. W. R i c h a r d s , W. M. C r a i g and J . S a m e s h i m a , P r o c . Nat.

A c a d . Sci. W a s h i n g t o n 4 , 387 (1918); C h e m . E n g . N e w s 34, 2887 (1956).

IV. G. Heyne, T h e s i s , R o s t o c k , 1 9 3 5 .

Gallium(lll ) Bromid e

GaBr3

Ga + lV²Br² = GaBr³

69.7 239.8 309.5

M e t a l l i c Ga i s h e a t e d in a s t r e a m of N² o r C 0² l a d e n with B r² v a p o r , a c c o r d i n g t o K l e m m a n d T i l k ' s m e t h o d . A w a t e r - c l e a r m e l t f o r m s f i r s t , b e c o m i n g y e l l o w to r e d - b r o w n , due t o d i s s o l v e d B r², w h e n a l l t h e Ga h a s r e a c t e d . W h e n t h e b r o m i n a t i o n i s c o m - p l e t e , t h e G a B r³ i s d i s t i l l e d in a n i n e r t , B r ²- f r e e g a s s t r e a m into a r e c e i v e r and t h u s s i m u l t a n e o u s l y f r e e d of d i s s o l v e d B r².

F i s c h e r and J i i b e r m a n n p r e p a r e d v e r y p u r e G a B r³b y v a c u u m s u b l i m a t i o n in q u a r t z e q u i p m e n t .

PROPERTIES:

C o l o r l e s s , v e r y h y g r o s c o p i c c r y s t a l s . M . p . 121.5°C, b . p . 279°C; d 3 . 6 9 .

REFERENCES:

W. K l e m m a n d W. Tilk, Z. a n o r g . a l l g . C h e m . 207, 161 (1932).

W. F i s c h e r and O. J i i b e r m a n n , Z . a n o r g . C h e m . 227, 227 (1936).

846 Ε . D O N G E S

Gallium(lll ) Iodid e

Ga 69.7

1V2I2 = 380.8

G a l³ 450.5

G a l l i u m iodide i s p r e p a r e d by K l e m m and T i l k ' s m e t h o d in t h e a p p a r a t u s shown in F i g . 2 4 9 . M e t a l l i c Ga i s p l a c e d in t h e c e n t e r s e c t i o n of t h e t u b e and t h e s t o i c h i o m e t r i c quantity of I² in t h e r i g h t s i d e f l a s k . After e v a c u a t i o n and s e a l i n g at a, I² i s s u b l i m e d b a c k and f o r t h o v e r t h e Ga, h e a t e d to t h e r e a c t i o n t e m p e r a t u r e , u n t i l t h e c o n v e r s i o n i s c o m p l e t e . T h e g a l l i u m r e a c t s with a c l e a r l u m i ­ n o u s f l a m e .

T h e iodide i s p u r i f i e d by F i s c h e r and J u b e r m a n n ' s m e t h o d in w h i c h it i s v o l a t i l i z e d in v a c u u m , u s i n g q u a r t z e q u i p m e n t .

sealing site

to pump

gaUium

F i g . 2 4 9 . P r e p a r a t i o n of gallium(III) i o d i d e .

PROPERTIES:

P a l e y e l l o w , h y g r o s c o p i c c r y s ­ t a l s , fuming in a i r . T h e m e l t i s o r a n g e - b r o w n . M . p . 212°C, b . p . 346°C; d 4 . 1 5 .

REFERENCES:

W. K l e m m and W. Tilk, Z. a n o r g . a l l g . C h e m . 207, 161 (1932).

W. F i s c h e r and O. J i i b e r m a n n , Z. a n o r g . a l l g . C h e m . 227, 227 (1936).

I. D. C o r b e t t and R. K. M c M u l l a n , J . A m e r . C h e m . Soc. 77, 4217 (1955).

Galliu m (II) Chlorid e an d Galliu m (II) Bromid e

GALLIUM (II) CHLORIDE

T h e c o m p o u n d i s p r e p a r e d a c c o r d i n g to M i e s c h e r a n d W e h r l i , by p a s s i n g d r y HCl o v e r m e t a l l i c Ga w h i c h i s gently h e a t e d in a P y r e x t u b e . P a r t i a l f o r m a t i o n of highly v o l a t i l e G a C l³ r e s u l t s . Heating t h e r e a c t i o n p r o d u c t w i t h e x c e s s Ga m e t a l in a fused, e v a c u a t e d P y r e x t u b e g i v e s p u r e G a C l².

1 6 . G A L L I U M , I N D I U M , T H A L L I U M 847 S o m e Ga r e a d i l y s e p a r a t e s on r e s u b l i m a t i o n , due to p a r t i a l d e c o m p o s i t i o n of G a C l² into G a C l³ and G a .

P R O P E R T I E S:

F o r m u l a w e i g h t 1 4 0 . 6 3 . M . p . 170°C, D i s p r o p o r t i o n a t e s to G a C l³ and Ga a b o v e 200°C.

G A L L I U M (II) B R O M I D E

M i e s c h e r and W e h r l i r e p o r t p r e p a r a t i o n of G a B r², in a m e t h o d i d e n t i c a l t o t h a t u s e d f o r G a C l², but e m p l o y i n g a s t r e a m of d r y C 0² s a t u r a t e d w i t h B r² i n s t e a d of HC1.

R E F E R E N C E:

E. M i e s c h e r and M. W e h r l i , H e l v . P h y s . A c t a 7, 331 (1934).

Galliu m Hydroxid e

G A L L I U M H Y D R O X I D E

L a u b e n g a y e r and E n g l e s t a t e t h a t c r y s t a l l i n e Ga(OH) ³ c a n b e p r e p a r e d a s f o l l o w s : a G a C l³ s o l u t i o n i s p r e c i p i t a t e d at 90°C w i t h N H³ s o l u t i o n , and t h e h y d r o x i d e i s w a s h e d t h o r o u g h l y and h e a t e d w i t h 6 m l . of w a t e r in a 1 5 - m l . a u t o c l a v e for about 89 h o u r s a t about 167°C. T h i s r e s u l t s in a v e r y fine p o w d e r with a m o i s t u r e c o n t e n t c o r r e s p o n d i n g r o u g h l y to t h a t f o r t h e t r i h y d r o x i d e and a c h a r a c t e r i s t i c , m e t a s t a b l e s t r u c t u r e , w h i c h slowly c o n v e r t s on h e a t i n g ( e . g . , a t o t a l of 166 h o u r s a t 170°C) to t h e d i a s p o r e s t r u c - t u r e of t h e m e t a h y d r o x i d e GaO(OH) ( s e e b e l o w ) .

P R O P E R T I E S:

F o r m u l a w e i g h t 1 2 0 . 7 4 . T h e c r y s t a l l i n e f o r m i s s o l u b l e in d i l u t e m i n e r a l a c i d s .

G A L L I U M M E T A H Y D R O X I D E

T h e c o m p o u n d GaO(OH), w i t h a d i a s p o r e s t r u c t u r e , i s o b t a i n e d in s l o w p r e c i p i t a t i o n of a s o d i u m g a l l a t e s o l u t i o n by a t m o s p h e r i c C O², a c c o r d i n g to B o h m and K a h a n .

M i l l i g a n and W e i s e r a d d j u s t sufficient N H³ s o l u t i o n t o a G a C l³ s o l u t i o n to r e d i s s o l v e t h e p r e c i p i t a t e d h y d r a t e d o x i d e and

8 4 8 Ε. D O N G E S

allow t h e s o l u t i o n to s t a n d in a d e s i c c a t o r o v e r c o n c e n t r a t e d H²S 0⁴. In about two w e e k s a l m o s t a l l t h e Ga p r e c i p i t a t e s a s t h e c r y s t a l l i n e m e t a h y d r o x i d e . It i s w a s h e d f r e e of CI"" i o n s by d e ­ c a n t a t i o n and d r i e d a t r o o m t e m p e r a t u r e .

A h y d r a t e d g a l l i u m o x i d e , p r e c i p i t a t e d at 30-40°C ( o r at 90°C) w i t h N H³ s o l u t i o n by L a u b e n g a y e r a n d E n g l e ' s m e t h o d , i s w a s h e d f r e e of f o r e i g n i o n s and h e a t e d with 6 m l . of w a t e r in a 1 5 - m l . a u t o c l a v e f o r about 100 h o u r s ( o r e v e n longer) a t 1 1 0 - 3 0 0 ° C ; t h i s y i e l d s t h e m e t a h y d r o x i d e a s s m a l l but w e l l - d e f i n e d c r y s t a l s w h i c h c a n b e d r i e d a t 105°C without d e c o m p o s i t i o n .

C r y s t a l l i n e Ga(OH) ³ m a y a p p e a r a s a m e t a s t a b l e i n t e r m e d i a t e a t about 170°C ( s e e a b o v e ) .

PROPERTIES:

F o r m u l a w e i g h t 102.73· T h e c r y s t a l l i n e f o r m d i s s o l v e s in d i l u t e m i n e r a l a c i d s . D i a s p o r e s t r u c t u r e ( E O^s s t r u c t u r e t y p e ) . Heating in a n a u t o c l a v e a b o v e 305°C c o n v e r t s it t o j 8 - G a²0³.

REFERENCES:

A. W. L a u b e n g a y e r and H. R. E n g l e , J . A m e r . C h e m . S o c 61_, 1210 (1939).

J . B o h m and G. K a h a n , Z. a n o r g . a l l g . C h e m . 2 3 8 , 350 (1938).

W. O. M i l l i g a n and Η. B. W e i s e r , J . A m e r . C h e m . S o c . 59, 1670 (1937); s e e a l s o R. Roy, V. G. Hill and E . F . O s b o r n , J . A m e r . C h e m . Soc. 74, 719 (1952).

Gallium(lll ) Oxid e

A hot, c o n c e n t r a t e d s o l u t i o n of N a H C 0³ i s a d d e d to a hot G a C l³ s o l u t i o n , a c c o r d i n g to t h e m e t h o d s of G o l d s c h m i d t , B a r t h a n d L u n d e and L a u b e n g a y e r and E n g l e . It i s t h e n b o i l e d u n t i l p r e c i p i t a t i o n of h y d r a t e d g a l l i u m oxide i s c o m p l e t e . T h e i n i t i a l l y g e l a t i n o u s p r e ­ c i p i t a t e i s w a s h e d f r e e of C I " i o n s w i t h hot w a t e r , w h i c h c a u s e s s o m e d e t e r i o r a t i o n .

The p r o d u c t i s a i r - d r i e d o n e h o u r a t r o o m t e m p e r a t u r e and t h e n h e a t e d t o 425°C in a P t c r u c i b l e . O v e r a p e r i o d of 24 h o u r s , t h e h y d r a t e d o x i d e c r y s t a l l i z e s a n d c a n s i m u l t a n e o u s l y l o s e i t s w a t e r to s u c h a n e x t e n t t h a t it finally c o n s t i t u t e s only about 1.5-4%

of t h e m a t e r i a l ; h o w e v e r , it often c r y s t a l l i z e s r a t h e r p o o r l y and s t i l l c o n t a i n s about 20% w a t e r e v e n a f t e r h e a t i n g f o r two w e e k s .

C o m p l e t e t h e r m a l d e h y d r a t i o n of a - G a²0³ i s i m p o s s i b l e , s i n c e t h e r e q u i r e d t e m p e r a t u r e s c o n v e r t it to £ - G a²0³.

PROPERTIES:

F o r m u l a w e i g h t 1 8 7 . 4 4 . V e r y s l i g h t l y s o l u b l e in w a t e r , slowly r e a c t s w i t h d i l u t e m i n e r a l a c i d s . C o r u n d u m s t r u c t u r e (D51 t y p e ) . Heating at 600°C in a i r p r o d u c e s s l o w m o n o t r o p i c c o n v e r s i o n to

£ - G a²0³. On h e a t i n g in a n a u t o c l a v e u n d e r w a t e r v a p o r a b o v e 305°C c o n v e r t s to j 3 - G a²0³, below 305°C, to GaO(OH) ( s e e a b o v e ) , d 6.44.

β -GALLIUM (III) OXIDE

K l e m m and Von Vogel c l a i m t h a t h e a t i n g in a i r to t e m p e r a t u r e s of at l e a s t 1000-1250°C i s n e c e s s a r y to c o n v e r t w a s h e d h y d r a t e d oxide to c o m p l e t e l y a n h y d r o u s , w e l l - c r y s t a l l i z e d £ - G a²0³.

L a u b e n g a y e r and E n g l e s t a t e t h a t c o m p l e t e l y a n h y d r o u s j 8 - G a²0³ c a n b e p r e p a r e d by a u t o c l a v e h e a t i n g of h y d r a t e d g a l l i u m oxide u n d e r w a t e r v a p o r f o r 74 h o u r s at 420°C.

PROPERTIES:

M . p . 1740°C. I n s o l u b l e in d i l u t e and c o n c e n t r a t e d m i n e r a l a c i d s . M o n o c l i n i c o r r h o m b i c c r y s t a l s , d 5 . 8 8 .

REFERENCES:

V. M. G o l d s c h m i d t , T. B a r t h and G. L u n d e , S k r . A k a d . Oslo 1925, No. 7, 2 4 .

A. W. L a u b e n g a y e r and H. R. E n g l e , J . A m e r . C h e m . Soc. 6 1 , 1210 (1939).

W. K l e m m and H. U . von Vogel, Z . a n o r g . a l l g . C h e m . 219, 45 (1934); s e e a l s o R. Roy, V. G. Hill a n d E . F . O s b o r n , J . A m e r . C h e m . Soc. 74, 719 (1952).

Gallium(l ) Oxid e

G a20

G a²0³ + 4Ga = 3Ga^sO

187.4 278.9 466.3

A s a m p l e of G a²0³ i s t r i t u r a t e d with e x c e s s fused G a . T h e m i x t u r e i s p l a c e d in a c o r u n d u m b o a t a n d h e a t e d u n d e r v a c u u m in a q u a r t z a p p a r a t u s p r o v i d e d w i t h a c o l d f i n g e r , a c c o r d i n g to t h e

8 5 0 Ε . D O N G E S

m e t h o d of B r u k l and O r t n e r and K l e m m and Von Vogel. A t r a p c o o l e d with Dry Ice m u s t b e i n s e r t e d b e t w e e n p u m p and a p p a r a t u s to p r e v e n t Hg f r o m c o n d e n s i n g on t h e c o n d e n s e r . Slow h e a t i n g i s n e c e s s a r y to a v o i d s u d d e n G a²0 s u b l i m a t i o n (which b e g i n s at 500°C)and c o n s e q u e n t b u m p i n g of p a r t of t h e G a^g0³- G a m i x t u r e into the c o n d e n s e r .

K l e m m and Schnick r e p o r t t h a t only a f t e r r e p e a t e d v a c u u m d i s t i l l a t i o n o v e r e x c e s s m e t a l l i c Ga d o e s t h e p r o d u c t a c q u i r e t h e oxygen c o n t e n t c a l c u l a t e d for G a²0 .

PROPERTIES:

F o r m u l a weight 155.44. B r o w n - b l a c k p o w d e r . N o t i c e a b l e v o l a ­ t i l i z a t i o n at 600°C in an i n e r t g a s s t r e a m at 1 a t m . and at 500°C in high v a c u u m . Stable in d r y a i r . D e c o m p o s e s in v a c u u m at 700°C to G a²0³ and G a .

REFERENCES:

A. B r u k l and G. O r t n e r , Z. a n o r g . a l l g . C h e m . 2 0 3 , 23 (1931).

W. K l e m m and H. U. von Vogel, Z . a n o r g . a l l g . C h e m . 219, 45 (1934).

W. K l e m m and J . Schnick, Z . a n o r g . a l l g . C h e m . 226, 353 (1936).

Gallium(lll ) Sulfid e

I- 2Ga + 3S = Ga²S³

139.4 96.2 235.6

Sulfur v a p o r i s p a s s e d o v e r m e t a l l i c Ga h e a t e d t o 1200-1300°C in a s t r e a m of N², a c c o r d i n g to B r u k l and O r t n e r ' s m e t h o d ; t h e Ga i s c o n v e r t e d t o yellow G a²S³. T h e s u l f u r i s p a s s e d t w i c e to e n s u r e c o m p l e t e r e a c t i o n , t h e p r o d u c t b e i n g p o w d e r e d b e t w e e n p a s s e s .

Hahn and K l i n g l e r b e l i e v e t h a t t h e d i r e c t s y n t h e s i s of G a²S³ i s s i m p l e r with t h e a p p a r a t u s of K l e m m and Vogel ( p r e p a r a t i o n of GaS; s e e b e l o w ) . T h e r e a c t i o n t e m p e r a t u r e i s 1250°C in t h a t c a s e .

II. G a²0³ [2 Ga(OH)³] + 3 H²S = Ga²S³ 4- 3 H²0 [6 H²0 ]

187.4 [241.5] 102.2 235.6 54.1 [108.1]

In K l e m m and V o g e P s m e t h o d , G a²0³ i s h e a t e d in a s t r e a m of H²S (purified by liquefaction with C 0²) f o r 14 h o u r s at 600-700°C and finally f o r four h o u r s at 1200°C. F a i n t l y y e l l o w G a²S³ i s obtained, t h e c o l o r d e p e n d i n g on t h e p a r t i c l e s i z e .

Hahn and K l i n g l e r s t a t e t h a t G a²S³ i s p r e p a r e d m o r e r a p i d l y and at l o w e r t e m p e r a t u r e s by s t a r t i n g with G a ( 0 H )³ d r i e d at 150°C i n s t e a d of G a²0³. H e a t i n g f o r about 12 h o u r s b e l o w 550°C g i v e s a - G a²S³ w i t h z i n c b l e n d e s t r u c t u r e (B3 s t r u c t u r e t y p e ) , t h e h i g h - t e m p e r a t u r e m o d i f i c a t i o n , £ - G a²S³ with w u r t z i t e s t r u c t u r e (B4 s t r u c t u r e t y p e ) , b e i n g f o r m e d a t 600°C. T h e s t a b l e m o d i f i c a t i o n , a w u r t z i t e s u p e r s t r u c t u r e w i t h o r d e r e d d i s t r i b u t i o n of m e t a l a t o m s , f o r m s a f t e r h e a t i n g s e v e r a l d a y s a b o v e 1000°C.

PROPERTIES:

M . p . (in v a c u u m ) 1255°C. Slow d e c o m p o s i t i o n in a i r with evolution of H²S . d ( x - r a y ) ot f o r m 3.747, β f o r m 3 . 6 7 6 . T r a n s i ­ tion t e m p e r a t u r e 5 5 0 - 6 0 0 ° C .

REFERENCES:

A. B r u k l a n d G. O r t n e r , N a t u r w i s s . 1 8 , 393 (1930).

M o n a t s h . C h e m . 5 6 , 358 (1930).

H. Hahn and W. K l i n g l e r , Z. a n o r g . C h e m . 259, 135 (1949).

W. K l e m m and H. U. von Vogel, Z . a n o r g . a l l g . C h e m . 2 1 9 , 45 (1934).

W . K l e m m , K. M e i s e l and H. U. von Vogel, Z . a n o r g . a l l g . C h e m . 190, 136 (1930).

H. Hahn and W. K l i n g l e r , Z . a n o r g . a l l g . C h e m . 2 7 8 , 333 (1955).

H. Spandau a n d F . K l a n b e r g , Z. a n o r g . a l l g . C h e m . 2 9 5 , 300 (1958).

Gallium(ll ) Sulfid e GaS

G a + S = G a S 69.7 32.1 101.8

S o m e Ga i s w e i g h e d into a n 8 - m m . q u a r t z t u b e s e a l e d at one end, and t h e t u b e i s d r a w n out to a width of 2 m m . at a d i s t a n c e 5 c m . f r o m t h e l o w e r end a n d b e n t at a r i g h t a n g l e , a s d e s c r i b e d by K l e m m and Von Vogel. T h e s t o i c h i o m e t r i c a m o u n t of S for t h e f o r m a t i o n of GaS i s p l a c e d in t h e o p e n - e n d s e c t i o n a n d t h e t u b e s e a l e d u n d e r v a c u u m .

T h e s i d e c o n t a i n i n g t h e S i s t h e n h e a t e d s o a s t o fill t h e whole t u b e w i t h v a p o r . T h e Ga on t h e o t h e r s i d e m u s t b e h e a t e d to r e a c t i o n t e m p e r a t u r e with a b l a s t b u r n e r , s o m e 0² b e i n g a d d e d t o w a r d t h e end of t h e r e a c t i o n t o r a i s e t h e t e m p e r a t u r e .

When t h e s u l f u r h a s r e a c t e d c o m p l e t e l y , t h e G a s e c t i o n , w h i c h now c o n t a i n s GaS, i s c o o l e d with w a t e r to c o n d e n s e t h e b a l a n c e

852 Ε . D O N G E S

of t h e S. T h e r e a c t i o n t u b e i s t h e n m e l t e d off at t h e b e n d a n d GaS h e a t e d f o r half an h o u r in a c r u c i b l e f u r n a c e at 1100°C t o c o m p l e t e t h e r e a c t i o n . T h e GaS i s r e a d i l y r e m o v e d a f t e r o p e n i n g t h e t u b e .

PROPERTIES:

Yellow, leafy m a t e r i a l . Stable to w a t e r . C a n b e s u b l i m e d a t 900-950°C in high v a c u u m t o h e x a g o n a l p r i s m s ; m . p . 965°C.

Hexagonal l a y e r l a t t i c e , d ( x - r a y ) 3.916.

REFERENCES:

W. K l e m m and H. U. von Vogel, Z. a n o r g . a l l g . C h e m . 219, 45 (1934).

H. Hahn and G. F r a n k , Z. a n o r g . a l l g . C h e m . 278, 340 (1955).

H. Spandau a n d F . K l a n b e r g , Z . a n o r g . a l l g . C h e m . 2 9 5 , 300 (1958).

Gallium(l ) Sulfid e

I. GaS + Ga = Ga2S 101.8 69.7 171.5

D i r e c t s y n t h e s i s f r o m Ga and S i s i m p o s s i b l e . T h u s , e x c e s s fused G a i s t r i t u r a t e d w i t h GaS, m i x e d with G a²S³ to p r o m o t e b e t t e r w e t t i n g , a c c o r d i n g to t h e m e t h o d of K l e m m and Von Vogel, d e v e l o p e d by B r u k l and O r t n e r . T h e m i x t u r e i s p l a c e d in a c o r u n ­ d u m b o a t i n s e r t e d in a q u a r t z a p p a r a t u s , equipped with a c o l d f i n g e r , in high v a c u u m . T h e b o a t c o n t e n t s a r e h e a t e d t o 7 0 0 - 7 2 0 ° C . If t h e s e t e m p e r a t u r e s a r e e x c e e d e d , t h e s u b l i m e d G a²S h a s too low a s u l f u r c o n t e n t .

Π. 2 G a + H2S = Ga2S + H2

139.4 34.1 171.5 2.0

A c c o r d i n g t o G a s t i n g e r , G a²S i s o b t a i n e d by h e a t i n g m e t a l l i c Ga at r e d u c e d p r e s s u r e (10 m m . ) to 1 0 0 0 - 1 2 0 0 ° C in a s t r e a m of H²S . F i g u r e 2 5 0 s h o w s the a p p a r a t u s d e v e l o p e d for t h i s p u r p o s e . R e a c t i o n t u b e r ( 4 0 - 5 0 m m . in d i a m e t e r ) , c o n d e n s e r k and b o a t c a r r i e r s i , a s w e l l a s t h e diffusion unit dk⁹ a r e m a d e of q u a r t z . T h e a p p a r a t u s i s f i r s t filled with a r g o n a t A r , with s t o p c o c k s h^l9 and h⁵ and h⁷ c l o s e d and a l l o t h e r s o p e n . After t h e t u b u l a r f u r n a c e ro i s a d j u s t e d t o t h e p r e s c r i b e d t e m p e r a t u r e , b o a t c a r r i e r st i s p u l l e d out, and b o a t s c a r r y i n g t h e Ga i s p l a c e d on it a n d i n s e r t e d into t h e f u r n a c e , t h r o u g h w h i c h t h e s t r e a m of A r i s p a s s i n g .

F i g . 2 5 0 . A p p a r a t u s f o r p r e p a r a t i o n of G a²S by h e a t i n g m e t a l l i c Ga in a s t r e a m of H²S .

p r e s s u r e and r a t e of t h e H²S s t r e a m c a n b e a d j u s t e d by s u i t a b l e c h o i c e of c a p i l l a r i e s o¹ and c². M a n o m e t e r s m¹ a n d m² a n d flow m e t e r sm s e r v e to c h e c k t h e s e p r o c e s s p a r a m e t e r s . T h e diffusion unit dk d e p r e s s e s b a c k - d i f f u s i o n of G a²S s o t h a t it p r e c i p i t a t e s only at t h e w a t e r - c o o l e d c o n d e n s e r Κ

W h e n r e a c t i o n i s c o m p l e t e , t h e a p p a r a t u s i s r e f i l l e d with A r by c l o s i n g s t o p c o c k s h⁷ a n d h^x and o p e n i n g h^Sf a n d c o n d e n s e r k w i t h i t s p r e c i p i t a t e d G a²S i s w i t h d r a w n .

PROPERTIES:

G r a y to g r a y - b l a c k . O x i d i z e s s l o w l y in a i r with l i b e r a t i o n of H²S , t u r n i n g g r e e n i s h , d 4 . 1 8 .

REFERENCES:

W. K l e m m and H. U. von Vogel, Z . a n o r g . a l l g . C h e m . 219, 45 (1934).

A. B r u k l a n d G . O r t n e r , M o n a t s c h . C h e m . 5 6 , 36 (1930).

E . G a s t i n g e r , Z. N a t u r f o r s c h . 10b, 115 (1955) and d e t a i l e d p r i v a t e c o m m u n i c a t i o n s t o G. B r a u e r .

H. Spandau and F . K l a n b e r g , Z . a n o r g . a l l g . C h e m . 2 9 5 , 300 (1958).

S t o p c o c k s h², h^Q and h³ a r e t h e n c l o s e d , H²S i n t r o d u c e d t h r o u g h h⁷, and t h e unit c o n n e c t e d t o a v a c u u m p u m p by o p e n i n g Η ^τ. T h e

854 Ε . D O N G E S

Ammoniu m Gallium(lll ) Sulfat e

A G a C l³ s o l u t i o n i s e v a p o r a t e d to d r y n e s s w i t h t h e s t o i c h i o ­ m e t r i c a m o u n t of H²S 0⁴ ( F e i t ' s p r o c e d u r e ) and t h e s u l f a t e i s d i s ­ s o l v e d in w a t e r . S t i r r i n g s o l i d (NH⁴) gS0⁴ into t h e s o l u t i o n r e s u l t s in p r e c i p i t a t i o n of t h e a l u m a s a c r y s t a l l i n e p o w d e r . T r i v i a l a m o u n t s of i m p u r i t i e s r e m a i n d i s s o l v e d in t h e m o t h e r l i q u o r .

T h e a l u m i s p u r i f i e d by r e c r y s t a l l i z a t i o n f r o m w a t e r , w h i c h should not b e too hot in o r d e r t o a v o i d f o r m a t i o n of b a s i c s a l t s .

SYNONYM:

A m m o n i u m g a l l i u m a l u m .

PROPERTIES:

F o r m u l a weight 4 9 6 . 0 7 . C o l o r l e s s c r y s t a l s ; i s o m o r p h o u s with t h e c o r r e s p o n d i n g a l u m i n u m a l u m . Solubility at 25°C: 1 p a r t in 3.24 p a r t s w a t e r ; p r e c i p i t a t e s b a s i c s a l t s on h e a t i n g , d. 1.777.

REFERENCE:

W. F e i t , Angew. C h e m . 4 6 , 216 (1933).

Galliu m Selenid e

2Ga + 3Se = Ga²Se³, Ga + Se = GaSe

139.4 236.9 376.3 69.7 79.0 148.7

A c c o r d i n g to K l e m m and Von Vogel, G a³S e³ a n d G a S e a r e p r e ­ p a r e d by t h e m e t h o d given f o r GaS ( s e e p . 851). T h e r e a c t i o n p r o c e e d s with b r i g h t r e d i n c a n d e s c e n c e ( f l a s h e s of f l a m e ) .

Ga²Se

K l e m m a n d Von Vogel s t a t e t h a t G a³S e c a n n o t b e d i r e c t l y s y n t h e s i z e d f r o m t h e e l e m e n t s . H e a t i n g e q u i v a l e n t a m o u n t s of Ga and Se v i a t h e p r o c e d u r e o u t l i n e d f o r t h e p r e p a r a t i o n of GaS ( s e e p . 851) g i v e s only h i g h e r s e l e n i d e s c o n t a m i n a t e d w i t h m e t a l l i c G a . H o w e v e r , if t h i s i n t e r m e d i a t e i s p l a c e d in a c o r u n d u m b o a t w h i c h

8 5 5 i s i n s e r t e d into a q u a r t z r e a c t o r e q u i p p e d with a c o l d f i n g e r and i s h e a t e d in high v a c u u m , a s u b l i m a t e u n i f o r m t o x - r a y a n a l y s i s , and having t h e c o m p o s i t i o n G a³S e , i s p r o d u c e d .

PROPERTIES:

G a²S e³: B l a c k a g g r e g a t e , r e d w h e n g r o u n d . F a i r l y h a r d and b r i t t l e . M . p . 1020°C, d ( x - r a y ) 5 . 2 0 3 . B3 s t r u c t u r e t y p e (zinc b l e n d e ) .

G a S e : D a r k r e d - b r o w n , g r e a s y , l u s t r o u s l e a f l e t s . M . p . 960°C, d 5.03. H e x a g o n a l and r h o m b o h e d r a l m o d i f i c a t i o n s .

G a²S e : F o r m u l a w e i g h t 2 1 8 . 4 0 . B l a c k , d 5.02.

REFERENCES:

W. K l e m m and H. U. von Vogel, Z. a n o r g . a l l g . C h e m . 219, 45 (1934).

H. Hahn and W. K l i n g e r , Z. a n o r g . C h e m . 259, 135 (1949).

K. S c h u b e r t , E . D o r r e and M. K l u g e , Z. M e t a l l k u n d e 4 6 , 216 (1955).

Galliu m Tellurid e

A c c o r d i n g t o K l e m m a n d Von Vogel, G a²T e³ and G a T e a r e p r e - p a r e d in t h e m a n n e r d e s c r i b e d for GaS ( s e e p . 851).

PROPERTIES:

G a²T e³: F o r m u l a weight 5 2 2 . 2 7 . B l a c k , h a r d and f a i r l y b r i t t l e . M . p . 790°C, d 5.57.

G a T e : F o r m u l a w e i g h t 1 9 7 . 3 3 . B l a c k , soft, g r e a s y l u s t r o u s l e a f l e t s , e a s y to g r i n d . M . p . 824°C; d ( x - r a y ) 5 . 7 5 1 . B3 s t r u c t u r e t y p e (zinc b l e n d e ) .

REFERENCES:

W. K l e m m a n d H. U. von Vogel, Z . a n o r g . a l l g . C h e m . 2 1 9 , 45 (1934).

H. Hahn a n d W. K l i n g e r , Z . a n o r g . C h e m . 259, 135 (1949).

Galliu m Nitrid e

I- Ga + NH³ = GaN + 1V²H²

69.7 17.0 83.7 3.0

A c c o r d i n g to t h e m e t h o d of Hahn a n d J u z a , d e v e l o p e d by J o h n s o n , P a r s o n s and C r e w , GaN i s p r e p a r e d by h e a t i n g m e t a l l i c

856 Ε . D O N G E S

Ga in a c o r u n d u m b o a t for two h o u r s at 1100°C in a r a p i d s t r e a m of N H³ w h i c h h a s b e e n d r i e d o v e r Na. T h e p r o d u c t i s t h e n g r o u n d and h e a t e d s i m i l a r l y f o r a n o t h e r two h o u r s . P a l e g r a y , finely c r y s t a l l i n e GaN r e s u l t s .

II, (NH⁴)³GaF⁶ + 4 N H³ = GaN + 6 N H⁴F

237.8 68,1 83,7 222.2

A c c o r d i n g t o Hahn a n d J u z a , ( N H⁴)³G a F⁶ ( s e e p . 228) i s h e a t e d 10 m i n u t e s at 900°C in a s t r e a m of N H³, a n a l o g o u s l y t o t h e p r e p ­ a r a t i o n of InN ( s e e p . 866). P u r e , but yellow GaN r e s u l t s .

PROPERTIES:

Slowly d i s s o l v e d by hot c o n c e n t r a t e d H²S 0⁴ and hot c o n c e n ­ t r a t e d NaOH, but not by c o n c e n t r a t e d HC1, H N 0³ a n d a q u a r e g i a . Stable in a i r , s u b l i m e s u n d e c o m p o s e d a t 800°C. d 6.10. B4 s t r u c ­ t u r e t y p e ( w u r t z i t e ) .

REFERENCES:

H. Hahn and R. J u z a , Z. a n o r g . a l l g . C h e m . 244, 111 (1940); c o m ­ p a r e a l s o R. J u z a and H. Hahn, Z . a n o r g . a l l g . C h e m . 2 3 9 , 282 (1938); 244, 133 (1940).

W. C. J o h n s o n , J . B . P a r s o n s a n d M. C. C r e w , J . P h y s . C h e m . 36, 2651 (1932).

Galliu m Nitrat e

T h e p u r e h y d r a t e G a ( N O^a) ³· 8 H²0 , d e s c r i b e d by E i n e c k e and e a r l i e r a u t h o r s , i s difficult t o p r e p a r e . H o w e v e r , a n h y d r o u s G a ( N 0³)³i s r e a d i l y p r e p a r e d a s f o l l o w s .

G a l l i u m m e t a l o r oxide i s d i s s o l v e d in n i t r i c a c i d . T h e s o l u t i o n i s r e p e a t e d l y e v a p o r a t e d to a v e r y s m a l l v o l u m e and r e d i l u t e d with w a t e r s e v e r a l t i m e s u n t i l t h e c o n c e n t r a t e d s o l u t i o n no l o n g e r h a s t h e o d o r of t h e a c i d . It i s t h e n d i l u t e d w i t h enough w a t e r to f u r n i s h 26 g. of Ga p e r 100 m l . of s o l u t i o n . At t h i s c o n c e n t r a t i o n a spongy, c r y s t a l l i n e m a s s of Ga(NO3)3· x H²0 s e p a r a t e s f r o m t h e v i s c o u s s o l u t i o n a f t e r 1-2 d a y s . T h e c r y s t a l s a r e f i l t e r e d by s u c t i o n and s u c t i o n - d r i e d in a i r f o r a w h i l e . T h e m o t h e r l i q u o r s t i l l c o n t a i n s a c o n s i d e r a b l e quantity of Ga, due t o t h e high s o l u ­ b i l i t y of t h e s a l t , and m a y b e r e u s e d o r w o r k e d u p . T h e c r y s t a l s a r e d r i e d in a s t r e a m of a i r , f i r s t a t r o o m t e m p e r a t u r e a n d t h e n at 40°C. T h e d e h y d r a t i o n i s c o m p l e t e a f t e r about two d a y s .

857

PROPERTIES:

W h i t e p o w d e r . Y i e l d s a c l e a r s o l u t i o n w i t h w a t e r ; v e r y s o l u b l e .

REFERENCES:

E . E i n e c k e , D a s G a l l i u m , 1937, p . 9 8 .

G. B r a u e r and U. S p o r k e r t , 1958, u n p u b l i s h e d .

Galliu m Phosphide , Arsenid e an d Antimonid e

Ga + P, As, Sb = GaP, GaAs, GaSb

69.7 3L0 74.9121.8 100,7 144.6 191.5

G o l d s c h m i d t r e p o r t s p r o d u c i n g t h e a b o v e t h r e e c o m p o u n d s v i a t h e following m e t h o d s .

G a P ( o r a n g e - y e l l o w , h a r d n e s s 5) i s f o r m e d by h e a t i n g h y d r a t e d g a l l i u m o x i d e in a s t r e a m of H², s a t u r a t e d with Ρ v a p o r , at 500°C.

G a A s ( d a r k g r a y , h a r d n e s s 4.2) i s f o r m e d by h e a t i n g G a²0³ in a s t r e a m of H² c o n t a i n i n g A s v a p o r . M . p . 1238°C.

G a B i h a s not y e t b e e n p r e p a r e d ; fusion of e q u i m o l a r q u a n t i t i e s of Ga a n d Bi at 600°C r e s u l t s only in a m i x t u r e of t h e two e l e m e n t s . All t h r e e c o m p o u n d s c r y s t a l l i z e in B3 s t r u c t u r e t y p e (zinc b l e n d e ) .

REFERENCES:

V. M. G o l d s c h m i d t , S k r . A c a d . O s l o 1926, No. 8.

W. K o s t e r a n d B. T h o m a , Z . M e t a l l k u n d e 4 6 , 291 (1955).

Indiu m

C r u d e i n d i u m o b t a i n e d , for e x a m p l e , a s a b y p r o d u c t of t h e New J e r s e y Z i n c r e f i n i n g p r o c e s s c o n t a i n s 2 - 5 % i m p u r i t i e s , about 0.8%

P b , 0.5% Zn, 0.5% Sn, 0 . 0 1 - 0 . 1 % Cu, and 0 . 0 1 - 0 . 0 5 % F e . Since Zn s e p a r a t e s t o g e t h e r w i t h t h e In in t h e s u b s e q u e n t e l e c t r o l y t i c r e ­ fining, c r u d e i n d i u m i s f i r s t f r e e d of Zn a s f o l l o w s : it i s h e a t e d a t 800-1000°C in a n i r o n t u b e c l o s e d a t o n e end a n d sufficiently long t o p r e v e n t s p r a y l o s s e s . S t e a m i s blown t h r o u g h t h e m e l t , by m e a n s

8 5 8 Ε. DONGES

of a n a r r o w p i p e , for 15 m i n u t e s . T h e z i n c v o l a t i l i z e s a l m o s t q u a n t i t a t i v e l y a s t h e o x i d e , and t h e r e s i d u a l i n d i u m c o n t a i n s only 0.008% Zn.

ELECTROLYTIC REFINING

C r u d e i n d i u m i s c o m m i n u t e d by r o l l i n g and c u t t i n g , and d i s ­ s o l v e d in w a r m , d i l u t e s u l f u r i c a c i d c o n t a i n i n g 1 0 0 - 2 0 0 g. H²S 0⁴/ l i t e r to m a k e t h e e l e c t r o l y t e s o l u t i o n . T h e t e m p e r a t u r e , q u a n t i t y a n d c o n c e n t r a t i o n of t h e a c i d a r e s u c h t h a t s o m e In r e m a i n s b e h i n d with t h e P b , Sn and Cu, but h y d r o l y s i s of t h e In i s p r e v e n t e d . P l a t i n u m foil o r g a u z e s e r v e s a s t h e a n o d e and s h o u l d b e a r r a n g e d p a r a l l e l to t h e c a t h o d e . A t h i n p i e c e of In foil, if a v a i l a b l e , i s u s e d a s t h e c a t h o d e ; o t h e r w i s e , highly p o l i s h e d Al foil ( r i n s e d w i t h benzine) i s e m p l o y e d . E v a p o r a t i o n of t h e b e n z i n e l e a v e s a t h i n , h a z y , oil f i l m w h i c h l a t e r f a c i l i t a t e s r e m o v a l of s e p a r a t e d In. T h e Al c a t h o d e s h o u l d b e s o m e w h a t l a r g e r t h a n t h e a n o d e and i t s e d g e s c o a t e d with a t h i c k c o a t of w a x to p r e v e n t In f r o m c r e e p i n g a r o u n d and s e p a r a t i n g on t h e r e a r s i d e ; t h i s would c o m p l i c a t e r e m o v a l of In. E l e c t r o l y s i s i s c o n d u c t e d at 20-35°C with a c u r r e n t d e n s i t y of 1 a m p . / 1 0 0 cm? Smooth d e p o s i t i o n i s a i d e d by h o u r l y a d d i t i o n of 1 m l . of 1% g e l a t i n o r c a r p e n t e r ' s g l u e s o l u t i o n p e r l i t e r of s o l u t i o n .

T h e s e p a r a t e d In i s finally fused t o a b u t t o n a t 600-800°C u n d e r a m i x t u r e of 1 : 1 KCN and NaOH. It i s 99.95% p u r e .

PROPERTIES:

A t o m i c weight 1 1 4 . 7 6 . S i l v e r y w h i t e , highly l u s t r o u s , v e r y soft m e t a l . Stable only in d r y a i r . M . p . 156.17°C, b . p . a b o v e 1450°C;

d 7 . 3 1 . A6 s t r u c t u r e t y p e . H a r d n e s s about 1.2.

REFERENCES:

F . E n s s l i n , Die C h e m i e 55, 347 (1942) and s u p p l e m e n t a r y p e r s o n a l c o m m u n i c a t i o n s , 1 9 4 8 . C o m p a r e a l s o F . E n s s l i n , M e t a l l und E r z 37, 4 0 1 (1940).

Indium(lll ) Chlorid e

I. I n²0³ + 3SOCl² = 2InCl³ + 3 S 0²

277.5 356.9 442.3 192.2

T h e c o m p o u n d i s p r e p a r e d by t h e m e t h o d g i v e n for G a C l³ ( s e e p . 843) a c c o r d i n g t o Hecht, J a n d e r and S c h l a p m a n n . A n a r r o w e r (9 m m . I.D.) t u b e with g r e a t e r w a l l t h i c k n e s s (3 m m . ) s h o u l d b e