40 IIYPONITEITES : PROPERTIES AND PREPARATION BY 



voiiiently got l)y dissolving the froslily prejoarcd hydrated 

 solid salt in water. Sodium iodide or j^otassium iodide and the 

 silver salt will also furnish a solution of alkali liyponitrite. 

 To get a solution for precipitating purposes, Thum proceeded 

 in an indirect way, first preparing a solution of hyponitrous 

 acid and then adding enough sodium hydroxide to make the 

 solution neutral to Phenolphthalein, an effective but very waste- 

 ful process. Kirschner also wanting a solution for precipitating 

 purposes, used sodium chloride and silver liyponitrite which, in 

 a complex and wasteful w^ay, he made yield a solution that, 

 though mixed with much chloride and nitrate, was practically 

 free from silver. 



Sodium hyponitrite. 



In 1878 Menke gave full analyses of crystals of a stable 

 salt having the composition of sodium hyponitrite with 6 HoO in 

 the molecule, which he had prepared by deflagrating in an iron 

 crucible a mixture of sodium nitrate and iron filings, keeping 

 the product at a red heat for an hour in a fire of charcoal 

 rather than of gas, boiling the mass with water, filtering off 

 iron oxide, evaporating, and leaving to crystallise. He makes 

 no reference in his paper to the large amount of sodium 

 hydroxide he must have liad to deal with, though this should 

 have seriously affected the procedure. In 1882 Zorn submitted 

 Menke's method to apparently very thorough trial and failed 

 to get the least trace of hyponitrite by it. But he found that 

 ferrous hydroxide acting on a solution of sodium nitrite did 

 produce sodium hyponitrite (in solution). His suggestion that 

 Menke had mistaken carbonate for hyponitrite takes no account 

 of the fact that the nitrogen and water in the salt were repeat- 



