66 HYPONITRITES I PROPERTIES AND PREPARATION BY 



tiously with dilute sulpluiric acid, and then tested, or preci- 

 pitated by silver sulphate, away from the light as far as 

 practicable, and the precipitate washed in the dark and con- 

 verted into the acid for testing, a solution will be obtained 

 which will not blue in the least the iodide reagent for an hour 

 or ni ore, in the dark and provided the constituents of the 

 reagent are pure enough and i^roperly used.* 



Against the view, which may be advanced, that hyponitrous 

 acid becomes nitrous acid through oxidation by the air, I must 

 point out that it is difficult to admit that, if the nitrous acid 

 has such origin, it should form so very slowly. A way presented 

 itself to me of deciding the point so far as the exclusion of 

 nitrous acid goes ; it has, however, in ray opinion, not served 

 to do so. If, in preparing sodium oximidosulphonate, the sul- 

 phur dioxide is used in excess, every trace of nitrite ought, 

 presumably, to get sulphonated ; if then the oximidosulphonate 

 is fully hydrolysed into oxyamidosulphonate, as it presumably 

 can be, then, in the conversion of the latter salt into hyponi- 

 trite and sulphite by potassium hydroxide there will be no 

 oximidosulphonate present to simultaneously revert to nitrite 

 and sulphite. Therefore, the silver hyponitrite from such a 

 source should be obtainable absolutely free from nitrite, and 

 should furnish a solution of hyponitrous acid also free from 

 nitrous acid. Such silver hyponitrite I endeavoured to pre- 

 pare, and then tested the acid got from it. The compli- 

 cation presented itself that such an acid is not quite free from 



*My way of applying the test is tliat followed by Warington {Chem. News, 1885, 51, 

 39), cxcejDt that, having potassium iodide of high quality, I used it instead of Trommsdorf's 

 zinc iodide solution. In the dark, a blank test will rem tin for hours without the leixst 

 blueing. Acetic acid has no advantage over pure sulphuric or hydrochloric acid. 



