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that d i r e c t l y o b s e r v e d in the s u c c i n o n i t r i l e - c a m p h o r s y s t e m .8 The a u t h o r s would like to a c k n o w l e d g e the a s s i s t ance of M i s s D e n i s e M a z e with both the X - r a y and m e t a l l o g r a p h i c w o r k . W o r k w a s p e r f o r m e d in the A m e s L a b o r a t o r y of the U.S. A t o m i c E n e r g y C o m i s sion. C o n t r i b u t i o n No. 3129. 1. J. D. Verhoeven:Met. Trans., 1971,vol. 2, p. 2673. 2 F. Wembergand B Chalmers.Can. J Phys., 1952,vol. 30, p.488. 3. P. J. Ahearnand M. C Flenungs.Trans. TMS-AIME, 1967,vol. 239, p. 1590. 4. F. R. Mollardand M. C. Flemings:Trans. TMS-AIME, 1967,vol. 239, p. 1967. 5. J. L. Dassel:Dendritic Solidification m Unidirectionally Frozen Tin-Bismuth Alloys, UmversltyMicrofilms,Ann Arbor, Mich., 1969 6. M. E. G|icksmanand R. J. Schaefer:Acta Met., 1966,vol. 14, p. t t 26. 7. R. Trtvedt Acta Met., 1970,vol. 18, p. 287. 8. L. R. Mornsand W. C. Wmegard:J. Cryst. Growth, 1967,vol. 1, p. 245.

Mass Spectrometric Study of the Thermodynamic Properties of the Ag-Sn System T E T S U O YAMAJI AND EIICHI KATO h study of the t h e r m o d y n a m i c p r o p e r t i e s of the A g Sn liquid a l l o y s h as b e e n m a d e with the c o m b i n a t i o n of a K n u d sen c e l l and a m a s s s p e c t r o m e t e r . Th e m a s s s p e c t r o m e t r i c a p p a r a t u s , Knudsen c e l l a s s e m b l y , e x p e r i m e n t a l p r o c e d u r e , and t e m p e r a t u r e m e a s u r e m e n t t e c h n i q u e s w e r e e s s e n t i a l l y the s a m e a s h a v e b e e n p r e v i o u s l y d e s c r i b e d . 1 In t h i s study, a l u m i n a Knudsen c e l l s with a thin g r a p h i t e l i n e r and g r a p h i t e K n u d sen c e l l s w e r e u s e d . T h e d i m e n s i o n s of the a l u m i n a c e l l s w e r e 19 m m OD by 19 m m high with 15 m m ID and a lid t h i c k n e s s of 1 r a m . T h e o r i f i c e d i a m e t e r w a s 0.7 m m giving the r a t i o of s u r f a c e a r e a to o r i f i c e a r e a of 450:1. Th e d i m e n s i o n s of the g r a p h i t e c e l l s w e r e 18 m m OD by 17 m m high with a 12 m m ID and a lid t h i c k n e s s of 3 m m . The o r i f i c e d i a m e t e r w a s 0.8 m m and t h e r a t i o of s u r f a c e a r e a to o r i f i c e a r e a w a s 225:1. T h e a l l o y s w e r e p r e p a r e d i n s i t u by m e l t i n g t o g e t h e r a t o t a l amount of 7 to 10 g of the c o m p o n e n t m e t a l s . T h e p u r i t y of the m e t a l s w a s 99.999 pct. P r i o r to t h e r e c o r d i n g of any d at a, the t e m p e r a t u r e of the K n u d s e n c e l l w a s r a i s e d to about 1250~ and held f o r 15 t o 20 m i n . Th e ion c u r r e n t s of s i l v e r and t i n w e r e t h e n m e a s u r e d and t h e t e m p e r a t u r e w a s l o w e r e d to a new v a l u e . T h e m e a s u r e m e n t s w e r e t a k e n at s u c c e s s i v e l y l o w e r t e m p e r a t u r e s . T h i s p r o c e d u r e w a s r e p e a t e d until constant ion