Standard free energy of formation of NiAs $$\bar S$$
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1. R. Hultgren, P. D. Desai, D. T. Hawkins, M. Gleiser, and K. K. Kelley: "Selected Values of the Thermodynamic Properties of Binary Alloys", ASM, Metals Park, OH, 1973. 2. K.T. Jacob, Can. Met. Quart., 1981, vol. 20, pp. 89-92. 3. K.T. Jacob: unpublished research. 4. J.P. Coughlin: "Contribution to the Data on Theoretical Metallurgy", Bull. U.S. Bur. Mines, 1954, no. 542, p. 80. 5. C.B. Alcock and S. Zador: Electrochim. Acta, 1967, vol. 12, pp. 673-77. 6. K.T. Jacob: J. Electrochem. Soc., 1977, vol. 124, pp. 1827-31. 7. H.K. Hardy: Acta Metall., 1953, vol. 1, p. 202. 8. G. K. Sigworth, J. F. Elliott, G. Vaughan, and G. H. Geiger: Can. Met. Quart., 1977, vol. 16, pp. 104-10.
-1.2
e-
:E X
Standard Free Energy of Formation of NiAsS
-1.3 r
:i
~o
_.o
D.C. LYNCH -1.4
-1.5
log "6"Mn/(1-XMn )2 = -0.4536 -1.0802XNi I
t
t
A
0.6
0.7
0.8
0.9
--XNi---~ Fig. 4--Variation of log yM./(1
-
XMn) 2
with alloy composition.
If this relation is assumed to be valid for high manganese alloys, then the excess Gibbs energies of mixing in the liquid Ni-Mn system can be represented by a subregular model: 7 AG s = XN~Mn(-32,010XM. - 49,410XNi) AG~i =
-66,810XZn + 34,800X3.
AG~n = -14,610X2i - 34,800X3i
J mol ~ [9]
mol -~
[10]
J mol -~
[11]
J
These data are useful in calculating deoxidation equilibria and the partitioning of manganese between alloy and slag in pyrometallurgical processes. The activity coefficient of manganese at infinite dilution at 1683 K, relative to pure liquid manganese as the standard state, is 0.029. This contrasts with a value of unity for the activity coefficient given by Sigworth et al 8 in their tabulation of thermodynamic data on dilute nickel alloys.
The arsenic bearing minerals niccolite (NiAs), maucherite (NillAS8), rammelsbegite (NiAs2), and gersdorffite (NiAsS) are found in nickel sulfide ores. The ore, after concentration, is roasted and then smelted in a reverberatory furnace, electric furnace, or flash smelting furnace. The As not liberated as A s 4 0 6 vapor during roasting, concentrates during smelting in the matte, and depending on the copper content of the matte, arsenic can concentrate in the nickel sulfide phase produced upon solidification. Once As enters the nickel sulfide phase it follows the nickel into the anodes, where 0.5 wt pct is not uncommon) The As is removed during electrolytic refining where it concentrates in the electrolyte. The arsenic must be removed from the electrolyte to prevent its physical entrainment in the cathode. Arsenic and many of its compounds are volatile, and thus it is feasible to eliminate the As during roasting. Recent investigations with arsenious copper concentrates have helped identify the conditions which lead to retention of arsenic.2 If this retention is to be minimized, thermodynamic data for As and its compounds will be necessary to perform the pertinent calculations. This study examines the standard free energy of formation of NiAsS. Yund examined the Ni-As-S system at 723, 873, and 973 K. 3 The NiAsS compound as shown in the p
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