IMIDOSULPHOXATES. 99 



salt, and imparts coiirmiKJUsJy to tlie \Nasb-waters «mall quantities of 

 a mercury sodium imidosnlphonate — aj)[)ai'ently the same as that got 

 by digesting mercuric oxide in a sohition of mercuric disodium imido- 

 snlphonate and perhaps 0[HgN(S03]Sr;»),,]^,. These waters are neutral 

 or faintly alkahne, and when eva.porated a- little on the water-bath 

 yield small qusmtities of micaceous crystals. This reaction appears to 

 be expressed by the equation : — 



2Hg( OHgS03)2NHgN(803Na),,+ UHo- OLHgNlSOsNa)^, 



-f2HN(ö03HgO),,Hg. 



Oxymercuric hydrogen imidosuljjhonate is an anhydrous salt. 

 Already dried in an ordinary desiccator, it loses, when further dried at 

 100° or above, 0'7 to 0*8 per cent, of water. It may be heated in 

 dried air to 180° or higher Avithout changing. Only a little below a. 

 dull red heat does it decompose, and then slowly gives water, nitrogen, 

 and sulphur dioxide. At this temperature it is yellow, but Avhen 

 cooled it resinnes the white colour of the undecomposed salt. At the 

 softening point of hard glass it melts to a, dark red liquid and eifer- 

 vesces, yielding sublimates of mercury metal, mercurous and mercuric 

 sulphates, and some other mercuric salt not sulphate and apparently 

 nitrogenous. It seems impossible, even in a vacuum, to decompose it 

 completely before the mercury sulphates themselves partly decompose. 

 The first o-avses sfiven off consist of nitroîxen with half its volume or 

 more of sulphur dioxide — those coming after still contain nitrogen along 

 with sulphur dioxide and oxygen. When rapidly raised to a red heat, 

 the s:dt, at the moment of melting, effervesces almost explosively. 



Its reactions with sodium hydroxide and chloride, and with 

 trisodium imidosnlphonate are similar to those of oxymercuric sodium 

 salt ([). 106). Its basic or oxysalt character is thus clearly demon- 

 strated, independently of the evidence from its quantitative analysis. 



