Thermodynamic properties of solid Au-Zn alloys by atomic absorption spectroscopy
- PDF / 555,388 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 68 Downloads / 194 Views
~
i
i
i
i
i
l
I000
_
oo-
I
soo-
°
\
T-
l ' r
too-
1 ..~-_'3
~: 6ooF,'
,
",'
i ";
,' \
'
^\
ooIl,'o.! II
/I I
300
/
I l k
~
.
I 0.25
7
/"
.
.
.
.
.
.
: \
i,
J i t i i i O.30 0.:35 0.40 0.45 0.50 0.55 ATOMIC F R A C T I O N Z I N C
Fig. 1--A portion of the A u - Z n P h a s e d i a g r a m ,r S o l i d points a r e new data from this w o r k . I n p r e v i o u s p a p e r s ,"%~° t h e a u t h o r s h a v e r e p o r t e d the d e v e l o p m e n t of t h e t e c h n i q u e of a t o m i c a b s o r p t i o n s p e c t r o s c o p y to d e t e r m i n e t h e r m o d y n a m i c a c t i v i t i e s . A d v a n c e m e n t s i n i n s t r u m e n t a t i o n n n o w p r o v i d e an i m p r o v e d a b i l i t y to d e t e r m i n e p a r t i a l m o l a r q u a n t i t i e s . This s t u d y incorporates such determinations a n d prov i d e s a b a s i s f o r e v a l u a t i o n of the t e c h n i q u e a s a n i n d e p e n d e n t m e a n s of o b t a i n i n g t h e r m o d y n a m i c d a t a .
EXPERIMENTAL Alloy Preparation
Fifteen-gram ingots were p r e p a r e d by melting accurately w e i g h e d a m o u n t s of A s a r c o 99.999 pct A u and 99.999 pct Zn in evacuated and sealed ~-in. diam silica t u b e s , a n d q u e n c h i n g the m e l t s into l i q u i d n i t r o g e n . T h e resulting rods were weighed and, as t h e m e a s u r e d w e i g h t l o s s e s w e r e i n s i g n i f i c a n t , the a l l o y c o n c e n t r a t i o n s w e r e c a l c u l a t e d d i r e c t l y f r o m the w e i g h t e d c h a r g e s . T h e alloy rods were s w a g e d at r o o m t e m p e r a t u r e a n d v a c u u m a n n e a l e d f o r a m i n i m u m o f 72 h r at 9 0 0 ° K to e n s u r e h o m o g e n e i t y . E a c h a l l o y was m i l l e d u n d e r a l c o h o l to p r o d u c e a b o u t {- g of s m a l l c h i p s . T h e u s e of c h i p s w i t h i n the a b s o r p t i o n c e l l s e n a b l e d a l a r g e s u r f a c e of a l l o y t o be e x p o s e d , t h e r e b y e n s u r i n g r a p i d e q u i l i b r i u m of t h e a l loy w i t h the e n c l o s e d v a p o r p h a s e . VOLUME 2 , JANUARY 1971- 79
Absorption Cells The silica absorption cells were 8-in.-long cylinders with 1 - i n . diam high-ultraviolet-transmission s i l i c a windows s e a l e d at e a c h e n d . The cell b o d i e s e a c h h a d a s m a l l side t u b e f o r l o a d i n g the s a m p l e a n d f o r e v a c uation. C e i l s were cleaned with chromic a c i d , t h o r oughly r i n s e d with distilled water, a n d f l a m e d r i e d u n d e r v a c u u m . A b o u t ~- g o f a l l o y c h i p s w a s l o a d e d into the c e l l a n d the c e l l e v a c u a t e d t o 10 - s t o r r o r better and s e a l e d . Apparatus A d e t a i l e d d e s c r i p t i o n of the a t o m i c a b s o r p t i o n t e c h n i q u e a n d i t s i n s t r u m e n t a t i o n h a s b e e n r e p o r t e d by u s11 a n d only a s u m m a r y i s p r e s e n t e d h e r e . A s c
Data Loading...
