IMTDOSULPHONATES. JQ5 



The exposure in the vacuum wa.s for 40-45 hours. The furtlier 

 loss at 100° was the o-reatest obtainable in undried air, lons"er heating- 

 being followed very slowly by increase of weight. As analysed, the 

 salt shows nearly a tenth less than the water calculated. Efflorescence 

 of the sample was not noticed, but may have occurred to a slight 

 extent. The main cause of the deficient finding is without doubt, 

 however, fixation of some of the crystallisation- water or of atmospheric 

 moisture by hydrolysis. 



Oxjimercuric sodinm imidosulphonate. — In the preparation of this 

 salt, when the sodium imidosulphonate is taken in double molecular 

 proi)ortion to the mercuric nitrate, that being the calculated proportion, 

 the process works well. The highly acid motlier-liquor retains much 

 of the salt in solution, but will let it fill if nearly neutralised with 

 sodium hydroxide, nnd then contains scarcely any other mercuric or 

 imidosulphonic salt. There is, however, no necessity to adhere closely 

 to the calculated proportions. Provided that the sodium salt is neither 

 in quantity great enough to redissolve the precipitate as mercuric 

 disodium salt nor so small as to leave the nitrate in much excess, the 

 process will succeed ; but it is better to use too little than too much of 

 the nitrate, above .all should its solution contain any quantity of free 

 acid. Any precipitation which water alone would cause of oxynitrate 

 in the solution of mercuric nitrate, is prevented by the presence of the 

 sodium imidosulphonate, since this salt forms its basic mercury 

 derivative by liberating half the nitric acid of the nitrate that it de- 

 composes, and this acid is much more than enough to keep any 

 remaining nitrate from passing into oxynitrate, and, consequently, the 

 washed precipitate proves to be always free from nitrate. It may be 

 washed sufficiently with water, which only very slightly acts upon it, 

 and may then l)e dried, either on paper or better on a tile. 



On attemj)ting to form a third and intermediate mercury sodium 



