SODIUM OR POTASSIUM : EDWAED DIVEES. 39 



destruction of some silver liyponitrite was thus avoided. In tliis 

 he was evidently mistaken, having overlooked the fact that it is 

 silver oxide, just as it is mercuric oxide, which hecomes decom- 

 posed, the liyponitrite or any otlier acid radical ])eing untouched 

 hy the hydroxylamine in alkaline solution. Whether, therefore, 

 mercuric oxide, or silver nitrate, or mercuric nitrate is used 

 and the precipitated metal then separated, the result is just the 

 same in concentrated alkaline solutions, except that the drop- 

 ping in of a solution of the nitrate is more easy to carry out than 

 stirring up with mercuric oxide. Where the alkaline solution 

 is very weak the use of mercury compounds is not without 

 ohjection, Ix'cause in this case a little mercuric oxide remains 

 dissolved. But whether silver or mercury oxide is employed, 

 the result is unsatisfactory ; for, as Thum has pointed out, 

 hoth these oxides generate nitrite in destroying hydroxylamine. 

 Not, however, that Thum himself found this fact to tell against 

 the use of mercuric oxide, for he was apparently successful in 

 purifying silver liyponitrite from nitrite by thorough washing 

 and reprecipitation, and was, therefore, independent of the pre- 

 sence of the produced nitrite. But Berthelot and Ogier, Paal 

 and Kretschmer, and I myself have not had that success, and 

 to get silver liyponitrite free from all trace of nitrite, I have 

 found it necessary to l)egin hy precipitating it in the ahsence 

 of nitrite. Nevertheless, far from casting doul)t upon Tlium's 

 success, I hold him to have proved his silver salt to have been 

 some of the purest ever prepared, l)y the account he has given 

 of the properties of hyponitrous acid. But, after all, no one 

 will be disposed to deny the superiority of sodium to mercuric 

 or silver oxide for removing hydroxylamine from the solution. 

 An almost pure solution of sodium hyponitrite can be con- 



