151 



a new investigation as to the equilibria in this system appeared to 

 us as being very desirable. Tiie residts obtained thus far, which 

 differ in some respects from llie dnt'i alieady known, will be stated 

 here in brief. 



2. The theoretical points of view which guided us here are the 

 same as those described in the system Pb — S — '). 



In order to find out whether cuprous oxide forms with cuprous 

 sulphide a stable phase-pair and also lo measure the SO,-pressures, 

 a very intimate mixture of these suh.stances was heated in a porcelain 

 tube connected witli an open manometer and a mercury air-pump. 

 The heating took place in a Heraeus oven; the measuring of the 

 temperature was carried out with a Pt-PtRli-lhermocell which had 

 been carefully set on the meliing points of tin, lead, zinc, antiraon}' 

 and silver and which was checked a few times during the experiments. 



The CujO was obtained by lednctioii of an alkaline (JuSO^ solution 

 with glucose, it was dried in a vacuum at 300' — 400° and contained 

 88.64% of Cu. The Cu^S was a preparation of Kahlbaum which, 

 mixed with a small quantity of sulphur, was heated for some time 

 in a current of hydrogen at 500° — 600° and so got the theoretical 

 composition. 



The equilibria pressui'es could be attained very readily' from both 

 sides; the values obtained from SOj-evolution and SOj-adsorption 

 only differed 2 — 3 mm. Also, afier evacuation the same jiressures 

 were always again obtained ; they are united in table I, where the 

 pressure is expressed in mm. mercury at 0°. 



T A B L E 1. 2CU2O + CU2S It 6Cu + SO2 (fig. 3 line III). 



1) W. Reinders, These Pioc. 23, 59Ü (1914). 



11* 



