1896.] P. C. Ray— On Mercurous Nitrite. 7 



The amount of mercary set free being equal to that contained in 

 the ic salt, quantitative proof of which has been given above. The 

 dissociation of mercurous nitrite is analogous to that of calomel :* 

 Hg^CI^^PIg + HgCV 



Diminution of pressure in one case playing the role of dilution in 

 the otiier ; nearly 22 per cent, of tlie salt, liowever, dissolves as such^ and 

 dilution has no further effect in increasing the proportion of dissocia- 

 tion. (Vide table, p. 4). 



The present compound throws additional light on the action of 

 nitric acid on the copper-mercury group of metals. It is now admitted 

 by chemists that " in their relation to nitric acid metals must be divid- 

 ed into two classes." To the former belong those which produce 

 ammonia and hydroxylamine from it ; e. g. Tin, Zinc, Cadmium, Iron, 

 Aluminium, Potassium, &c., while the latter includes Copper, Silver, 

 Mercury and Bismuth. These seem to enter into direct union with the 

 nitrogen of the acid, instead of displacing its hydrogen. The formation 

 of the nitro compounds of the fatty series by V. Meyer's method lends 

 additional support to this theory. This 7iitronic constitution of nitrous 

 acid, as Divers puts it, also explains the advantage of red or yellow 

 nitric acid in dissolving metals of the silver- mercury class. f 



i| + H I NO, + HO I NO, = ^1 N0' + ^*^'^- 

 Indeed, the presence of nitrous acid seems to be sine qua non for 

 the dissolution of metals like silver, mercury, &c., us was first pointed 

 out by Russell. J This chemist also showed thot when silver dissolves 

 in nitric acid, " silver 7ii7riYe is formed in quantity, partly in solution 

 in the silver nitrite liquor, partly as crystals." The stability of silver 

 nitrite in presence of strong nitric acid is noteworthy, as ordinary 

 nitrites are decomposed even by the weakest acids. The niti-onic 

 nature of silver nitrite affords a ready explanation of this apparent 

 anomaly. 



Acworth and Armstrong in their classical researches found " that 

 " the amount of gas [NO] obtained by decomposing silver nitrite by 

 " nitric acid varies according to the strength of the acid, being greater 

 ^^ the iveaker the aatZ " (the italics are ours) again "no amount of 



* Harris and V. Meyer's recent experiments fully bear out the conclusion arriv- 

 ed at by Odling years ago. See " Ueber den Molekularzustand des Calomedamp- 

 fes" Berichte : 27 (1894) p. 1482. 



t Divers : Chem. Soc. Journ. for 1883 Trans., p. 443; also ibid. Trans, for 1885, 

 p. 231. 



X " On the action of Hydrogen on Silver Nitrate," Chem. Soc. Journ. Trans 

 [ 2.] xii. 3. 



