170 



S. HADA; HOW MERCUROÜS AND 



cognised. Thus, in the Kraut-Jörgensen edition (1875), we are only 

 told, with Proust as authority, that the solution of mercurous nitrate 

 oxidises in the air, the record of the volatilisation of mercury being 

 suppressed, while the error as to oxidation is retained. The fact of the 

 volatilisation of mercury appears in none of the modern dictionaries or 

 handbooks. It is probably on the authority of Proust that Mendeléeff 

 has stated, in the passage already quoted, that mercurous salts, parti- 

 cularly in acid solutions, are oxidisable by the air. Kane (1838 ; 

 Annalen, 26; Ann. Chim. Phys. [2], 72, 215) observed that half 

 basic mercurous nitrate is partly converted by long boiling with fresh 

 quantities of water into mercury and mercuric salt, the volatilisation 

 of the mercury not being noticed by him. Hose's views (1841 ; 

 Annalen, 39 106) have already being referred to. He is clear on 

 the point that mercurous nitrate, continuously boiled with water, be- 

 comes mercuric nitrate and mercury, but his purely theoretical paper 

 contains other statements which cannot be accepted. According to 

 him, both the mercury and the mercuric nitrate occur in the precipi- 

 tate which water forms from mercurous nitrate, but that is clearly not 

 the case. Gmelin on his own authority (Handboolc) makes a state- 

 ment which, for the unfortunate reader, serves fully to eftace any im- 

 pression caused by Kane's statement given above, for he tells us, 

 " On boiling the monobasic [normal] salt with water till the residue 

 turns grey, the filtrate contains but a, mere trace of mercuric salt." 

 This is no misprint ; it is repeated m Gmelin- Kraut. I had better, there- 

 fore, at the cost of repetition, state here that in an open vessel of good 

 modern glass or porcelain, mercurous nitrate boiled with water for 

 hours produces mercuric nitrate in solution, mercury vapour, usually 

 no globules under the solution, and a basic mercurous precipitate which 

 does not become grey when strong day-light is excluded, but remains 

 dull yellow with perhaps a tinge of green ; as before stated, the 



