AMIDOSULPHONIC ACID. 225 



method until amidosul phonic acid itself becomes easily purchasable, as 

 it should henceforth be. 



Preparation from hydroxylamine sulphate. — Raschig's account of 

 this process, using the hydrochloride, is brief and as follows : — ' Saturate 

 an aqueous solution of hydroxylamine hydrochloride with sulphur 

 dioxide, allow it to stand some time, and then evaporate till a pellicle 

 of crystals forms. A large quantity of the acid crystallise« out by 

 cooling, and the mother-liquor yields a little more, but mixed with 

 ammonium sulphate.' Krafffc and Bourgeois (1892) used the solution 

 of hydroxylamine hydrochloride very concentrated, saturated it with 

 sulphur dioxide to begin with and, for a day or two, supplied more 

 as needed. In this way, they got the acid to crystallise without any 

 evaporation, to the extent of fully three-sevenths of the calculated 

 quantity. Although sulphur dioxide takes some hours to complete 

 its action on hydroxylamine, it acts rapidly at first, and occasions a 

 sensible rise of temperature. Cold checks its action ; at 0° there 

 appears to be none. Saturation of the hydroxylamine solution at this 

 temperature with sulphur dioxide is sufficient, once for all, unless it is 

 a very concentrated one, or is left exposed to the air. Some of the 

 amidosul phonic acid gets hydrolysed, if the solution is evaporated on 

 the water-bath, but not appreciably by evaporation in the cold. 



Two points had to be investigated, one being as to whether the 

 acid of the hydroxylamine salt had any influence upon the reaction, 

 and the other, whether hydroxylamine and sulphur dioxide suffer 

 complete conversion into amidosulphonic acid, or yield other products, 

 such as ammonium sulphate, nitrogen, or nitrous oxide. The out- 

 come of these investigations was that the action of sulphur dioxide is 

 quantitatively the same upon the hydrochloride, the sulphate, and the 

 base itself, and that ammonium hydrogen sulphate is a direct product 

 of its action, and the only one besides amidosulphonic acid. Very 



