J 54 



If, by removing eacli tiirie the SO, formed, we allow this reaction 

 to lake place eoiiiiilelel} , either a mixture of CiiS and Cn,S or one 

 of Cu,S and CiiSO^ will remain. 



On increasing the temperature the first will be converted 

 completely into Cu„S with eliuiination of sulphur according to 

 2CuS^CUjS 4" S- Tl'is reaction has been completely confirmed by 

 the experiments of Preuner and Brockmöller. 



The mixture of Cu^S and CuSO^ will form Cu,0 with evolution 



of SOj and yield pressures appertaining to the monovariant equilibrium : 



Cu^S + 2 CuSO, :^ 2 Cu,0 + 3SÜ, .... (II) 



Of this process the reaction product must be a mixture of CujO 

 and CiijS or of Cu^O and CUSO4 according to whetlier it contained 

 originally an excess of Cu^S or of CuSO^. 



In the first case will take place the reaction 



2Cu,0 + Cu,S:;t6Cu + SO, (Ill) 



which leads to the equilibria pressures mentioned in table I. 



Mixtures of Cu,0 and CuSO^ will, at a continued increase of 

 temperature, form as a third phase either CuO, or an intermediate 

 basic copper sulphate between CuO and CuSO^. In connexion with 

 the experiments of Wöhi.er and his coadjutors') it was probable 

 that a role is played here by the basic sulphate CuO . CuSO^ so 

 that we shall obtain first of all the monovariant equilibrium : 



4CuS0, + Cu,0 :^ 3CuO CuSO, -f SO, ... (IV) 

 and then 



CuOCuSO, + Cu,0 ;f: 4CuO + SO, . . . . (V) 



Finally, we will, therefore, have left a mixture of CuO and CujO 

 or of CuO and CuO . CuSO^. The latter will then dissociate according 

 to : CuO . CuSO^ 7t 2CuO -|- SO3, whereas at a still higher temperature 

 occurs the dissociation of CuO into Cu,0 -{- '). 



6. The above considerations have been completely confirmed by 

 our pressure measurements. 



Pressures appertaining to the monovariant equilibrium: 3CuS-|-. 

 CuSO, ^ 2Cu.,S 4" 20O, were obtained by starting from an intimate 

 mixture of CuS and CuSO^. 



The CuS04 was obtained by dehydrating pure crystallised CuSO^ . 

 511,1) an I heating ai 300° — 400 in order to eliminate any free 

 s I. Ill i.' Mcid i-\i'iiiually preseai. CuS was prepared by precipitating 

 a f' ill; arnl -oiit.iu if CuSO, wiili H,S at the ordinary teuipe- 



') Blt der deiilschen ciiem. Uesellscliatt 41, 7w3 (1908). 

 2) L. WöHLER. Zeilschr. f. Eleklroch. 12, 784 (1906). 



