150 



vibrating particles (comp. the end of tlie preceding §) we can say 

 nothing about jjö and must confine ourselves to a conclusion con- 

 cerning h„(f. However this may be, it seems rather probable that 

 the finest lines in the spectrum of the sun are caused by relatively 

 small quantities of the absorbing gases. 



It ought also to lie remarked that the problem is, strictly speaking, 

 less simple than we have put it here. We have reasoned as if a small 

 quantity of an absorbing vapour were present in front of a radiating 

 body giving rise to a continuous spectrum. In this spectrum there will 

 then be a tine absorption line. In reality, however, if there is very 

 rare calcium vapour in a certain layer, there will be vapour of 

 somewhat greater density at a greater depth in the sun's atmosphere. 

 For a satisfactory theory of the phenomena it would be necessary 

 to explain why this latter vapour does not give rise to a broader 

 absorption line, but must rather be considered as belonging to the 

 mass to which the continuous spectrum is due. 



Chemistry. — "Egui/ihria in (he si/steii) Cu — »S' — O; the roasting 

 reaction process loith copper." By Prof. W. Rkinders and 

 F. GouDRTAAN. (Communicated by Prof. Hoogewerff). 



(Communicated in the meeting of May 29, 1915.) 



1. In the metalluigy of copper the I'eactions, which may occur 

 between the roasting products of the partly burnt copper ore, play 

 an important role; in special conditions they can lead in a direct 

 manner to the separation of metal. Usually it is assumed that these 

 reactions take place according to the subjoined equations ') : 

 Cu,S + 2 CuO = 4 Cu + SO, 

 Cu,S + 2 Cu,0 = 6 Cu + SO, 

 Cu,S + 3 CuO = 3 Cu -f Cu,0 + SO, 

 Cu,S + 6 CuO = 4 Cu,0 + SO, 

 Cu,S + CuSO, = 3 Cu + 2 SO, 

 Cu,S + 4 CuSO, = 6 CuO + 5 SO, . 

 Systematic researches as to this process, which seems very com- 

 plicated owing to the large number of possible phases, are exceedingly 

 scarce. The only observations worth mentioning are those of R. 

 ScHENCK and W. Hempelmann") ; they determined ^/Alines for mixtures 

 of CuoS — Cu,0, CujS — CuSO, and Cu — CuSO,. As these observations 

 are incomplete and their conclusions in many points unsatisfactory, 



1) ScHNABEL, Handb. der Metallhüttenkunde I 176 (1901). 



2) Metal! und Erz, 1, 283 (1913). Z. f. angew. Chemie 26, 646 (1913). 



