304 E. DIVERS AND T. HAGA : 



lipon a nitrite was found out by Raschig, when trying to prove 

 anotlier point (sect. IV. a.). He added the nitrite to excess of 

 sulphur dioxide, both being in very dilute and well cooled 

 solution, evaporated down find neutralised the solution with 

 chalk, and again evaporated the filtered solution. After much 

 potassium sulphate had crystallised out, potassium amidosulphate 

 was finally obtained, as proof that hydroximidosulphate had 

 been formed at an earlier stage. Our own experiments have 

 yielded us an earlier product of the degradation of this com- 

 pound. 



At the time when Kaschig published his observation, we 

 published {J. Oh. Soc, 1887, 51, 659) one of ours, that silver 

 nitrite and mercurous nitrite, when decomposed by sulphur 

 dioxide solution, yield a substance answering to the copper test 

 for hydroxylamine. This we now know to be hydroxyamido- 

 sulphuric acid, but at the time we took it to be hydroxylamine 

 itself. We have also found that, after adding a dilute solution 

 of sodium nitrite to excess of a cooled solution of sulphur dioxide 

 and then blowing out of the solution the residual sulphur diox- 

 ide by a current of air, enough hydroxyamidosulphate (hydrolysed 

 hydroximidosulphate) is present to be easily identified by the 

 copper test for it. A hydroxyamidosulphate is distinguishable 

 from hydroxylamine in applying this test by finding that the 

 mother-liquor of the cuprous oxide (which need not be filtered 

 off) gives sulphurous acid when acidified (this Journal III, 225). 



Though less successful than Claus's experiment, Raschig's 

 method is serviceable for showing that the alcohol used in that, 

 plays only a secondary part. While excess of nitrite is success- 

 fully used in that experiment, the sulphur dioxide must be in 

 excess in Raschig's method. To understand this, it has only to 



