157 



8. This contradiction induced us to try and find the initial 

 melting points of mixtures of CujS and CuSO^ by the thermic 

 process. For this purpose they were heated in a glass tube placed 

 in an electric oven whilst the heating curve could be recorded with 

 a silver-constantane thermo-cell. The tube was furnished with an 

 exit tube; the gas developed during the measurement was thus 

 carried off, adsorbed in alkali and finally determined. The rise in 

 temperature amounted to 3° per minute; the starting of the fusion 

 was characterized by a very pronounced inflexion in the heating- 

 line. For instance, with a mixture of 25 grams of CuSO, and 25 

 grams of Cu,S (about 1 mol. CuSO^ to 1 mol. Cu,S) the constancy 

 of the temperature amounted to ± 5 minutes, after which a regular 

 rise of 2 — 3° per 1' again set in. With mixtures of different com- 

 position were obtained initial melting points which differed only 1 — 2°. 



The mean value amounts to 484°. During the observation thei-e 

 was evolved, when using 25 grams of mixture, on an average 160 

 mg. of SO,, from which we deduced that the mixture can have been 

 converted at most to the extent of 27„. The value found can, there- 

 fore, be but a very little too low. 

 p 



T. 3 CuS t CuSO^ ^ 2 Cu,S + Z SOj. 

 I. Cu,S + I CuSO^Ji 2Ci4^0 + 3 SO,. 



Fig. 2. 



As the fused mass evolves SO, very powerfully, jjeating in a 

 sealed apparatus was not possible. 



By exactly' the same method the initial melting points of ternary 

 mixtures of CiiSO^, Cu,S, and Cu^O were recorded. Also here, the 

 results obtained with mixtures of different composition only differed 



