286 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 12 



any given temperature the oxygen equilibrium pressure is dependent on the 

 composition of the soHd phase. 



The authors' results show that solid solutions are absent, and that the 

 following reactions may take place in the system: 



(1) 4CuO(5)-2Cu20(5) + 02(g) -AH, 



(2) 4CuO(5)^2Cu20(/ solution in CuO) + 02(g) — AH2 



(3) 4CuO(/ solution in Cu20)^2Cu20 {s)-\-02{g) — AH3 where AHi, AH2, and 

 AH3 are the heat quantities absorbed in each reaction. 



At 1080.2 °C and an oxygen equilibrium pressure of 402.3 mm. Hg, a eutectic 

 containing 72.7 mol per cent CU2O and 27.3 mol per cent CuO fuses. Below 

 this point, therefore, Reaction (1) takes place; above this point either Reaction 

 (2) or (3) takes place, dependent upon the quantity of oxygen originally 

 present in the solid and liquid phases. The pressure-temperature curves 

 for these reactions have been traced experimentally up to temperatures of 

 1085.0°, a metastable point, for Reaction (1); to 1232.5° for Reaction (2); 

 to 1231.3° for Reaction (3). 



Theoretically the course of these curves, which intersect at the quadruple 

 (eutectic) point of the system can be followed by means of the general equation 



dp/dt = An/Av 

 w^hich, under conditions of constant temperature and pressure, becomes 



dp/dt = 1/T.AH/AV 

 AHi remains substantially constant over the temperature range studied. 

 AH2 can be considered as the algebraic sum of AHi and of additional heat 

 absorbed by fusion of CU2O and of additional CuO to form the liquid solution. 

 AH2 is therefore greater than AHi and the value of dp/dt above the eutectic 

 point is always greater than that of the extrapolation of curve for Reaction 

 (1). Likewise A//^ is always less than A//, and the slope of the curve for 

 Reaction (3) is always less than that of the extrapolation of the curve for Re- 

 action (1). 



The curve for Reaction (2) is tangent to the curve for the condensed system 

 CuO (5), CuO(/) at the melting point of pure CuO; that for Reaction (3) 

 is tangent to the curve for the system Cu20(5), Cu20(/) at the melting point 

 of CU2O. The melting point of pure CuO has not been reached. 



The melting-point diagram for mixtures of the two copper oxides, under 

 equilibrium pressures of oxygen, has been established throughout the range 

 94.4 mol per cent CU2O to 45.9 mol per cent CU2O. 



Lower equilibrium pressures were determined in a fused silica tube reaction 

 chamber with a mercury manometer attached. Higher pressures were de- 

 termined with a furnace enclosed in a brass bomb, and with a caHbrated 

 Bourdon gage. Temperatures were measured by means of a platinum- 

 platinrhodium thermoelement. Purified electrolytic oxygen was used and 

 copper oxides were prepared from previously analyzed chemically pure me- 

 tallic copper. 



The paper was discussed by W. P. White. 



F. Wenner, J. S. Martin, and Nyna L. Forman: The electrical resistance 

 of the human body. (Illustrated; presented by Mr. Wenner). 



Measurements of the electrical resistance of the human body have given 

 results differing among themselves so radically that one seeking information 

 on the subject is led to question either the reliability of the work or the signifi- 

 cance of the values given. 



The difficulties encountered have had their origin mainly in those portions 



