on the Specific Weight of Chemical Compounds. 183 



Some few of these oxides do not agree, viz. Mn O, Sn O, 

 Mo O^ and Pb O^. For some oxides the atomic volume must 

 be assumed = 16, for others — 64. 



Dr. Kopp then shows the untenability of Schroder's theory 

 with lespect to the oxides, inasmuch as he has made an as- 

 sumption for almost every fact to be explained, and a theory 

 which recjuires as many or more assumptions than there are 

 facts to be explained is quite useless. 



The statements, with regard to the densities of the sulphurets, 

 are very insecure and variable, on account of the great diffi- 

 culty in obiaiiiing them in a sufficiently pure state. The num- 

 ber of assumptions required is therefore necessarily increased. 



