236 EDWARD DIVERS AND TAMEMASA HAGA ; 



tion of the salts, has lost its value. Berglund, by laborious processes, 

 prepared the barium salt by hydrolysing either the barium or the 

 mercury barium imidosulphonate, and from this obtained the acid and 

 the other salts. He gave himself unnecessary trouble through his belief, 

 founded on observation, that imidosulphonates have a great tendency to 

 pass at once into ammonium sulphate, instead of stopping at the stage 

 of amidosulphonates, although these, once formed, are stable enough. 

 Instead of describing Berglund 's, now obsolete, process, we will give a 

 very simple modification of it that may sometimes prove useful. 



Normal barium imidosulphonate, freed from alkali by re-precipi- 

 tation, is kept on the water bath, with very slightly more dilute 

 sulphuric acid than is equivalent to one-third of its barium, just so 

 long as a little of the filtered solution is found to yield barium 

 sulphate on boiling ; then, after filtering off and washing the barium 

 sulphate, the solution of amiclosulphonic acid is evaporated in the cold 

 over sulphuric acid. 



Nothing need he said of the preparation of the salts from the 

 acid. A line or two may be given to the direct preparation of the 

 sodium and potassium salts from the nitrite. If, in the preparation of 

 the acid from sodium nitrite, already described, the mother-liquor from 

 the sodium sulphate crystals is further evaporated, sodium amido- 

 sulphonate crystallises out, and can be thus obtained. But from the 

 smallness of the crystals and their great solubility, they are badly 

 obtained from an impure solution, and it is far better to prepare 

 the salt from purified acid and sodium carbonate. Raschig obtained the 

 potassium salt direct, in the above way. Other amidosulphonates 

 cannot be prepared by double decomposition of the alkali salts (see the 

 account of the silver salt, p. 239). 



All amidosulphonates (except the oxymercuric) are soluble in 

 water, the least soluble of them being the silver salt (Berglund). Most 



