450 TRANSACTIONS OF SECTION B. 
Wohler has determined the dissociation pressures of cupric oxide when 
heated. He has shown that solid solutions of cuprous oxide in cupric oxide 
are formed. His values therefore are somewhat lower than the highest disso- 
ciation pressures obtainable. 
Slade and Farrow have determined the dissociation pressures of cuprous 
oxide at temperatures and under conditions at which the mixture of two liquid 
phases mentioned above must necessarily have been present. These pressures 
are given in the subjoined table as points on the experimental curve ¢ g. 
From the sources mentioned the data have been collected and used to con- 
struct a temperature-composition and a temperature-pressure diagram which 
are attached to the paper. 
Table of numerical values of the data represented by the chief points on the diagrams. 
Tempera- | Composition 
Name ture Centi-|=oxygen con-| Pressure Explanation 
grade /tent per cent. 
Points 
a 1084 0:0 — | M.P. of pure Cu 
b 1065 0°39 -— Cu, Cu,O eutectic 
e 1195 2:26 — Invariant point. Phases 
present: Solid Cu,0, 
| liquidI. LiquidII. Gas. 
d 1210 11°16 -= M.P. of pure Cu,0 
e | ec. 1060 c. 14°8 c. 460 mm. | CuO, CuO eutectic 
f 2c, 1240 20°10 ?20atm. | M.P. pure CuO 
Curves | 
960 — 50 mm. either 
Bee | 1050 vk Biden. | As et curve of CuO 
[| 1070 is 458 mm. | | ssociation pressure 
| } 
| 
| 1205 —— 4mm.) Slade v. Farrow’s curve of 
pes (| 1240 _ 10mm. | dissociation pressure of | 
hae 1260 = 12 mm. the two liquid phases of 
| 1324 -- 25 mm. the Cu,0, Cu mixture. 
5. Equilibria of Reduction of Oxides by Carbon. 
By R. E. Suave and G. I. Hieson. 
The equilibrium pressures obtained when certain oxides are reduced by 
carbon have been determined. 
The reaction which takes place is of the type 
MO+C.>CO4+M 
where M denotes two equivalents of one of the following substances: V, Ta, 
Cr, B, Mn, Sn. 
In some cases a carbide is formed. This reaction is represented by the 
equation— 
2MO + 30 .>* M,C + 2C0. 
In the experimental method employed there was always an excess of the free 
metal present. In either case there are three components, M, C, and O, and 
four phases, CO, M, MO, and either C or M,C. Therefore, there is one degree 
“ om of the system. At each temperature there is a definite pressure 
of CO. ; 
The substance M was heated in an unglazed porcelain boat in vacuo, in the 
i Oi ti 
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