70 



DIVERS AND HAU A. 



Both iiiercury nitrates ure also precipitating agents, acting l\ere 

 as they do when added in excess to a solution of trisodinm imidosul- 

 phonate (p. 101). Mercuric oxide, especially the precipitated form, 

 reacts with it to give mercuric disodium imidosulphonate (p. 102). 

 Warmed with a moderately concentrated solution of the salt, the 

 mercuric oxide dissolves and, on cooling and standing, the solution 

 deposits crystals of the double salt. Silver hydroxide is rapidly 

 converted by solution of disodium imidosulphonate into the sparingly 

 soluble argentum disodium salt (p. 95) Cupric hydroxide is without 

 action. 



Evaporated on the water-bath with S(idium carbonate, or even 

 with acetate, disodiutn imidosulphonate is partly converted into triso- 

 dium imidosulphonate, while carbon dioxide or acetic acid escapes. 

 In the case of using acetate, therefore, there is presented the striking 

 phenomenon of a strongly acid vapour rising from ;i well-marked 

 alkaline liquor. 



In analysing the salt, we hydrolysed it by heating it with hydro- 

 chloric acid to 150° in sealed tabes for some hours, here following 

 Raschig in his annlysis of the potassium salts. The composition of 

 the salt is expressed by the fornuila — HN(S03N"a)o, (OHs)., the results 

 of analysis being — 



Sodium 



Sulphur 



Nitrogen 



Trisodium imidünalphoriate.— Thin salt is prepared from the di- 

 sodium salt by adding sodium hydroxide to its strong solution. It is 

 unnecessary to have the disodium salt pure and in crystals. After 

 following the process for getting this salt so far as to separate one 

 good crop of crystals of sodium sulphate, the liquor is diluted with 



