IMIDOSULPHOXATES. IQl 



Now this reaction can actually be realised, as already stated, but only 

 with difficulty :!nd in the presence of great excess of mercuric nitrate 

 solution, active probably by virtue of its free acid. In the direct 

 method of preparing the hydrogen salt, it is formed simultaneously 

 with half as much again of nitric acid as is produced when the sodium 

 salt is fanned. From this it would appear that there is a point — 

 difficult to determine by direct experimentation with nitric acid, 

 becjiuse of its liability to cause hydrolysis after a time, and of the 

 uncertainty in knowing when the sought-for change has occurred — 

 where, the nitric acid being in sufficient quantity along with the 

 mercuric nitrate, nitj-ogen takes or keei)s hydrogen in place of mercury, 

 and the second half of the sulphonic radicals, as well as the first, takes 

 mercuric oxide in place of sodium, just as it does in other cases even in 

 presence of free acid. 



Mercury sodinni inridosulplionates. — There are two mercury sodium 

 imidosulphonates. The monosodium salt is oxymercuric or basic, but 

 tlie disodium salt is normal, and corresponds in composition with the 

 potassium salt obtained Ijy Berglund. 



unless gradually added, mercuric nitrate causes, almost immedi- 

 ately, a white crystal !o-flocculent precipitate in solutions of the 

 trisodium imidosulphonate, which disap|)ears on agitation so long as 

 enough of the sodiinn salt remains to keep the mixture alkaline or 

 neutral. When this point is passed, preci])itati()n is pei'manent, and 

 ox ij mercuric sodiuiu salt is tlie product. When the nitrate is only added 

 till neutrality is reached or nearly reached, the liquor soon begins to 

 form small brilha.nt crysttils, or else will do so after some evaporation. 

 These crystals are normal mercuric disodium imidimdjdioiuite. Adding 

 solution of trisodium imidosnlphonate to that of mercuric nitrate, free 

 from any unnecessary excels of nitric acid, causes again, as already 

 stated, a white crystal lo-tl<3Cculent ])recipitate which, with sufficient 



