Thermodynamic properties of the liquid Ge-Cu and Ge-Au systems by mass spectrometry
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P. HAGER,
STANLEY
M. HOWARD,
AND
JOHN
H. JONES
The a c t i v i t i e s and p a r t i a l m o l a r heats of m i x i n g have b e e n d e t e r m i n e d for the liquid Ge-Cu s y s t e m at 1525~ and the liquid Ge-Au s y s t e m at 1400~ The e x p e r i m e n t a l technique cons i s t e d of a n a l y z i n g Knudsen cell effusates with a TOF m a s s s p e c t r o m e t e r . The ion c u r r e n t r a t i o s for the m o n o m e r i c vapor s p e c i e s were m e a s u r e d as a function of t e m p e r a t u r e and c o m p o s i t i o n and the t h e r m o d y n a m i c p r o p e r t i e s c a l c u l a t e d u s i n g a modified f o r m of the G i b b s - D u h e m e q u a t i o n s . Both s y s t e m s exhibited negative d e v i a t i o n s f r o m ideal b e h a v i o r . The r e s u l t s for the Raoultian a c t i v i t y coefficients can be p a r t i a l l y r e p r e s e n t e d by log YGe = -- 2.521X~u + 0.948
(0 _< XGe s 0.2)
log YOu = - 0 " 0 4 8 X ~ e - 0.466
(0 < X c u _< 0.2)
for the Ge-Cu s y s t e m at 1525~
and by
log 7Ge = -- 2.327X~u + 0.465
(0 _< XOe _< 0.35)
log 7Au = --0.510X~e - 0.489
(0 _< Xau _< 0.30)
for the Ge-Au s y s t e m at 1400~ An e x p e r i m e n t a l technique is p r e s e n t e d for d e t e r m i n i n g the c o n t r i b u t i o n of d i s s o c i a t i v e i o n i z a t i o n of p o l y m e r s p e c i e s to the m e a s u r e d m o n o m e r i c ion c u r r e n t r a t i o . The effect of d i s s o c i a t i v e ionization of the g e r m a n i u m p o l y m e r s p e c i e s p r e s e n t in the Knudsen ceil effusate was d e t e r m i n e d to be negligible.
IN a p r e v i o u s p a p e r 1 the
a u t h o r s have p r e s e n t e d t h e r m o d y n a m i c data for the liquid s y s t e m s Cu-Sn and CuAu obtained by the Knudsen c e l l - m a s s s p e c t r o m e t e r technique. Using the i o n - c u r r e n t r a t i o method d e v e l oped by Belton and F r u e h a n , 2 it was shown that, p r o vided p r o p e r e x p e r i m e n t a l c a r e is taken, v e r y p r e c i s e t h e r m o d y n a m i c data m a y be obtained. The e x p e r i m e n tal technique c o n s i s t e d of m e a s u r i n g the r a t i o of ion c u r r e n t s for the m o n o m e r i c v a p o r s p e c i e s in the Knudsen cell effusate as a function of t e m p e r a t u r e and alloy c o m p o s i t i o n . The Raoultian a c t i v i t i e s and a c t i v i t y coe f f i c i e n t s , and the i n t e g r a l and p a r t i a l m o l a r heats of m i x i n g were then c a l c u l a t e d by m e a n s of the following equations: Xl = Xl
log 71 = - J
log (I;Xl/I:Xz)
[1]
Xl d log ( I ; X , / I i X z )
[2]
Xz d
xl = 1 X2 = X2 log 72 =
] x2 = 1
Xl = Xl
H~r
fXzdI31~ X1 = 1
1 3 (l/T)
[4] X2 = 1
8 (l/T)
X2
-- rvY
[5]
: x , H y + x2
[6]
where Ii and I~ a r e the r e l a t i v e ion i n t e n s i t i e s for the m o n o m e r i c s p e c i e s of c o m p o n e n t s 1 and 2. In the p r e s e n t study the e x p e r i m e n t a l technique has been used to i n v e s t i g
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