62 HYPONiTKiTES ; thoperties and prepaeaticn by 



reddened litmus pajDer it Lecomes blue again. A solution of 

 the acid becomes neutral to litmus when only half enough 

 baryta water or alkali to form the normal salt has Ijeen added 

 (Zorn). Such a solution soon by decomposition acquires the pro- 

 perty of blueing red litmus paper. When neutral to litmus 

 the solution is also neutral to Phenolphthalein (Thum). Neu- 

 tralised with baryta, hyponitrous acid yields an acid salt when 

 its solution is very rapidly evaporated under reduced pressure, 

 crystalline and extremely unstable (Zorn). 



It decomposes silver carbonate, if not also lead and other 

 carbonates ; it also decomposes silver nitrate and sulphate. It 

 does not oxidise hydrogen iodide (iodide and starch reagent) 

 and is not oxidised Ijy iodine solution or by the air. It is 

 oxidised by nitrous acid and the stronger oxidising agents. No 

 way of deoxidising or hydrogenising hyponitrous acid is known ; 

 it entirely resists the action of sodium amalgam and also, 

 according to Thum, that of zinc and sulphuric acid. Ethyl 

 hyponitrite is reduced apparently by tin and acetic or hydro- 

 chloric acid to alcohol and nitrogen, accordiug to Zorn, but as, 

 also according to him, it is slowly decomposed by itself when 

 moist into nitrogen, alcohol, and aldehyde, there is sufficient 

 reason to doubt that this reduction by tin and acid is more 

 than the hydrogenisation of aldehyde. 



Hyponitrous acid slowly decomposes into nitrous oxide and 

 water. A strong solution soon effervesces, gently in the cold, 

 freely when heated, just like a solution of carbon dioxide, and 

 some hyponitrites in presence of only a little water effervesce 

 with an acid. A solution of one or two grams of the acid in a 

 litre of water kept in ice hardly falls noticeably in streugth in 

 one hour, but at 25-30° it may lose a sixth of the acid by 



