200 PROCEEDINGS OP THE AMERICAN ACADEMY 



XII. 



CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 

 HARVARD COLLEGE. 



ON THE OCCLUSION OF GASES BY THE OXIDES OF 



METALS. 



By Theodore William Richards and Elliot Folger Rogers. 



Presented May 10, 1893. 



In the course of an investigation upon the atomic weight of copper, 

 recently conducted in this Laboratory, it was noted that cupric oxide 

 prepared by the ignition of the nitrate always contains a considerable 

 amount of occluded gas, which is composed mainly of nitrogen.* 

 Cupric oxide prepared from the carbonate, on the other hand, appears 

 to possess no such property of occluding gases. Since the material 

 used by Hampe and others had all been made by the former method, 

 it was at once evident that the occluded gas contained in the oxide was 

 wholly responsible for the formerly accepted erroneous results for the 

 atomic weight of copper. 



The results of these experiments suggested the possibility that gases 

 might be occluded by all oxides prepared in this way from the nitrates. 

 It became a matter of much importance to test the point, for such 

 oxides have often furnished the starting point for determinations of 

 atomic weights. 



The method adopted in the present research was precisely similar 

 to that used in the case of the cupric oxide. Since it is by no means 

 certain that indefinite heating in a vacuum could drive out all the gas 

 from the compact, often crystalline compound under examination, the 

 material was dissolved in acids under such conditions that the gas 

 set free could be measured and analyzed. 



The simple apparatus needed has been described and explained in 

 the paper already quoted. The material to be investigated was placed 



* Theodore W. Richards, These Proceedings, XXVI. 281. In 1868 Frank 

 land and Armstrong pointed out this fact ; but their statement lacked definite- 

 ness, and has since been largely forgotten. 



