194 HADA; HOW M'ROUS & M'RIC SALTS CHANGE INTO EACH OTHER. 



a solution of mercuric nitrate, and the products to be mercurous nitrate 

 and mercuric sulphide nitrate. Probably, too, there is a quantitative 

 separation effected of the metallic mercury and the mercuric sulphide. 

 But, even so, this would not in itself be a proof of the matter in 

 question, because mercurous sulphide might well by double decom- 

 position with mercuric nitrate become mercuric sulphate and mercurous 

 nitrate, and then the former unite with more mercuric nitrate. Not- 

 withstanding that the two components of the mixture cannot be 

 quantitatively separated, the fact remains that mercury and mercuric 

 sulphide behave together just as does the supposed mercurous sulphide. 

 Thus, cold nitric acid, sp. gr. 1.2, does not by itself convert precipitated 

 mercuric sulphide into the white sulphide-nitrate, but does so if some 

 mercury is present. It is known too, that mercuric sulphide is 

 whitened by digestion with a solution of mercuric nitrate. 



In conclusion I wish to record gratefully my indebtedness to Dr. 

 Edwnrd Divers, F.E.S. for his guidance in carrying out this research, 

 and for the large part he took in putting the account of it together. 



