74 HYPONITRITES ; PROPERTIES AND PREPARATION BY 



oxygen of the air. Not always, however, does the change occur 

 in this striking and rapid way, its progress being gradual and 

 almost imperceptible till complete. 



Mercuric hyponitrite is decomposed by heat largely into 

 mercuric oxide and nitrous oxide, but partly into metal and 

 nitric oxide. 



Other Hyponitrites. 



Mercurous hyponUrile. — This salt has been prepared and 

 analysed by Thum {Taaug. Diss., Prag, 1893), who used sodium 

 hyponitrite and mercurous nitrate in obtaining it. The possi- 

 bility of getting it by the spontaneous decomposition of mercuric 

 h^^ponitrite has just been described. Eây has also evidently 

 obtained it in a very impure state, not further examined. It 

 can be prepared in the same Avay as mercuric hyponitrite, using 

 mercurous nitrate in place of mercuric nitrate. It is of a full 

 yellow colour, is blackened by even the weakest solution of 

 alkali, and is soluble in dilute nitric acid, from which it can 

 be precipitated by sodium carbonate. It is a stable salt, but is 

 blackened by bright light. Its decomposition by heat is like 

 that of the mercuric salt, except that much more metal is pro- 

 duced, as is natural. Composition ; (HgON).. 



Gapric hydroxide hy2:)onilrite. — This salt ^Yas described by 

 me in 1871 and was also obtained by Kolotow in 1890, but 

 was first fully examined by Tlium and has again been examined 

 by Kirschner. Being a basic salt, its precipitation from 

 normal sodium hyponitrite leaves an acid mother liquor, on 

 neutralising which much more of the salt precipitates. It is 

 of a bright pea-green colour and a very stable salt. It may 

 be boiled with water without losing its colour. It is decomposed 



