SODIUM OK, POTASSIUM I EDWAllD DIVERS. Oo 



moist precipitate retain their colour outside Avliilc drying in a 

 thermostat, but become greyish inside. Silver hyponitrite dis- 

 solved in solution of sodium or potassium hyponitrite decom- 

 poses on standing and very quickly on boiling, silver being 

 reduced and sodium nitrite formed in solution. 



Bright diffused light causes enough change in a few hours 

 — bright sunlight in a few minutes — to allow of nitrite being 

 detected. The colour change caused by light has been variously 

 described ; as a matter of fact, in the sufliciently pure salt under 

 water, it is such that the bright yellow hyponitrite becomes 

 covered with a somewhat bright brown flocculent substance, 

 closely like silver oxide which perhaps it is; the blackening or 

 greying which has been observed by others to be caused by 

 light must have been due to impurities, though time, as just 

 described, brings about greying of the salt. Silver hyponitrite 

 is least sensitive to light when dry and exposed to dry air. The 

 main change which occurs in the moist salt, slight as it is, is 

 evidently similar to that which heat causes. The salt prepared 

 by the oxyamidosulphonate method generally shows an unreal 

 stability, due apparently to presence in it of a trace of sulphite, 

 as will be explained when tlie properties of a hyponitrous acid 

 solution are being treated of (p. 63). For in that connexion it has 

 to be taken into consideration that, like many other precipitated 

 substances, silver hyponitrite is difficult to ol)tain of high purity. 

 The very slight atmospheric oxidation of moist silver hyponitrite, 

 described by Haga and me {J. Ch. Soc, 1884), I now regard 

 as being not the oxidation of the salt itself, but of nitric oxide 

 produced Ijy the very slowly decomposing salt, which is then 

 retained as nitrate and nitrite in the salt. The result will be 

 the same as if the salt itself oxidised. 



