AMIDOSULPHONIC ACID. 233 



nearly complete. With only half as much sulphuric acid present, 

 barium chloride takes half an hour to cause any precipitation, and this 

 remains very slight for a long time. In strong, neutral or alkaline 

 solutions, alkali amidosulphonates also retard, for a day or two, the 

 complete precipitation of a sulphite by barium chloride. Amido- 

 sulphonic acid with sodium changes into its sodium salt and hydrogen. 

 It dissolves zinc and iron (Berglund). It does not decompose an alkali 

 chloride or nitrate, when mixed with the salt in the damp state or in 

 solution. Heated dry with the salt, it causes decomposition, but then 

 the acid is itself decomposed. 



Amidosulphonic acid is decomposed with effervescence, even at 

 the ordinary temperature, by a mixture of concentrated sulphuric acid 

 and a nitrate or nitric acid, the gas being nitrous oxide. In this 

 respect, its behaviour is like that of imidosulphonic acid, which, in 

 1892, we fully described, on page 77 of our paper on Imidosidphonates 

 (This Journal, Q). Soon after issuing that paper, we recognised the 

 similarity of this reaction with that discovered by Franchimont (1887), 

 — that by which nitramide has recently been obtained by Lachmann 

 and Thiele (189(5). But we were, at that time, unable to study the 

 reaction further. Lachmann and Thiele have been the first to publish 

 the fact that amidosulphonic acid gives nitrous oxide when treated 

 with nitric and sulphuric acids. They also state that nitramide itself 

 cannot be got by the reaction, but they give no particulars. We, too, 

 have failed to get any nitramide, not, apparently, because it is decom- 

 posed after being formed, but because there is no action between the 

 nitric and amidosulphonic acids in a, freezing mixture. As already 

 mentioned, amidosulphonic acid is quite insoluble in strong sulphuric 

 acid and but little soluble in the dilute acid. Owing to this property, 

 we have been able to recover from a mixture of the acids, which had 

 been stirred up for nearly an hour, immersed in ice and salt, not only 



