The surface tension of liquid silver-copper alloys
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( g a s ) = CaS ( s l a g ) + 1 / 2 02 ( g a s ) w h e r e a s E q . [1] i s w r i t t e n a s A1OI.~ ( s l a g ) + 3 / 2 C ( g r a p h i t e ) + 1 / 2 N2 ( g a s ) = A1N ( s l a g ) + 3//2 CO ( g a s ) . B y a p p l i c a t i o n of t h e l a w of m a s s a c t i o n it i s s e e n t h a t K c y a n i d e , K}~arbide a n d s u l f i d e c a p a c i t y a r e p r o p o r t i o n a l to aCaO/~" Ca 0 5CN, a C a O / T C a C 2 , aCaO//VCaS (a = a c t i v i t i e s , T = a c t i v i t y c o e f f i c i e n t ) , r e s p e c t i v e l y . K n i t r i d e i s p r o p o r t i o n a l to aA1OI.5//TA1N . It i s e v i d e n t t h a t t h e a c t i v i t y / a c t i v i t y coefficient ratios involving the Ca containing compon e n t s i n c r e a s e w h e n c a l c i u m f l u o r i d e i s a d d e d to C a O A1203 m e l t , * )
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*It should be mentioned that the data on carbide solubility reported in this work and in previousliterature3'4 are completelyat variance with data of D. M. Edmunds and J. TaylorH on the reaction
Knitrid e = ( 0035 -" 0 015 ) wt~ otrn
CaO (solid oxide) + 2C (graphite) = CaCa(solidcarbide)+ CO (gas)
o~ o12 013 o'4 o:s o'.6 o'7 0'8 o~
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PCO' elm
Fig. 3--Plot of data in a c c o r d a n c e with Eq. [6]. 03
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slope = (12/26) Kcyonid e
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T h e a u t h o r s w i s h to t h a n k M i s s R u t t e n f o r h e r h e l p in p e r f o r m i n g the e x p e r i m e n t s .
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01Kcorbid e = ( 011 t 0 02 ) vd% Qtm
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Accordingto these authors the carbon monoxide pressureis 3.26 atm for this reaction at 1600~ and the acaO value for the 32 wt pct CaO, 32 wt pct AI~O3,36 wt pct CaF2 slag is approximately0.4. If these data were correct the CO pressure for the equilibrium between the four phasesmelt, graphite, gas, solid carbide would be 1.3 atm at 1600~ that is solid carbide shouldhave precipitated under all the atmospheresused. There was no indication that this happened. The equilibrium of reaction [8] has been measured previously1 by ourselvesyielding Pco = 0.029 atm at 1600~ This datum is very close to that computed from the available free energy data of CaO 12, CaC212and CO.13
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Fig. 4--Plot of data in a c c o r d a n c e with Eq. [7].
The following numerical values were obtained for K c y a n i d e , K n i t r i d e , K c a r b i d e (1600~ slag composit i o n 32 w t p c t C a O , 32 wt p c t A1203, 36 w t p c t C a F a )
1. K. Schwerdtfegerand H. G. Schubert: Arch. Eisenhuetten., 1974, voI. 45, pp. 649-55,905. 2. K. Schwerdtfegerand H. G. Schubert: Met. Trans. B., 1977,vol. 4B, pp. 535-40. 3. H. G. Schubert and K. Schwerdtfeger:Arch. Eisenhuetten., 1974, vo]. 45, pp. 437-39. 4. J. H. Swisher: Trans. TMS-AIME, 1968, vol. 242, pp. 2033-37. 5. R. Juza and H.-U. Schuster: Anorg. Chem., 1961, vol. 311, pp. 62-76. 6. A. Mitchell: Trans. TMS-AIME, 1968, vol. 242, pp. 2507-11. 7. W. A. Barber and C. L. Sloan: J. Phys. Chem., 1961, vol. 65, pp. 2026-28. 8. R. Juza, U. Landt, and H. Hansen: Anorg. Chem., 1967, vol
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