IMIDOSULPHONATES (2ND. PAPER). 213 



nitrate remaining insoluble, because of the nitric acid which is 

 generated. The equation expressing the reaction is — 



(4HgN0 8 ) 2 +H 2 + 2HN(S0 8 Na) 2 =0[Hg 4 TSr(S0 8 ) 2 ] 2 +4NaNO s +4HN0 8 . 



Of the sodium salt 1.05 grains, dissolved in about 150 ces. water, 

 added with stirring gradually to 4.5 grams mercurous nitrate in about 

 20 ces. water, gave a precipitate weighing 2.75 grams, and nitric acid 

 in solution weighing 0.33 gram, the ratio of these weights being in 

 accordance with the above equation. The precipitate was tested for 

 nitrate and sulphate, and none found ; and the nitric acid in 

 solution was measured by titration with sodium hydroxide, after 

 addition of excess of sodium chloride had been made. The mother- 

 liquor contained no sulphuric acid. 



The new salt is flocculent and quite white, and has the following 

 composition, expressed by 0[Hg' 2 N(S0 3 )fïg' 2 ] 2 ,6H 2 : 



Cale. Found. 



Mercury, 77.22 77.27 



Sulphur, 6.18 6.18 



It is free from sodium. Although it contains water, it loses very 

 little in weight at 100° or 120°, and part of that loss will be due to 

 volatilisation of mercury, for the salt becomes very grey. More 

 strongly heated, it becomes nearly black temporarily, soon growing 

 white again. Then, or while still black, the altered salt gives some 

 mercuric chloride, as well as mercurous chloride, when triturated with 

 a solution of sodium chloride. At an incipient red heat the whitened 

 altered salt fuses and effervesces, yielding nitrogen but no sulphur 

 dioxide. The black-red liquid consists mainly of the mercury 

 sulphates. 



Mercurous imidosulphonate dissolves in dilute nitric acid much 

 more readily than does mercuric imidosulphonate, and from the solu- 



