SODIUM OR POTASSIUM : EDWARD DIVERS. 65 



First, there is the unlikelihood that the cliazo radical, N:N, 

 should resolve itself into mono-nitrogen compounds, such as 

 NO, NH3, NO.OH, or (NOj.O, instead of (^V^O. Secondly, there is 

 the fact that time conges in as the condition of the production 

 of nitrous acid, and that a rise in temperature does not. Solu- 

 tion of hyponitrous acid of fair purity boiled or quickly 

 evaporated gives only nitrous oxide and water ; and only very 

 slowly and slightly does nitrous acid appear in a cold solution 

 of the purest acid. Thirdl}^, the more care taken to reduce and 

 exclude all nitrite in preparing the hyponitrous acid solution, 

 the longer will be the time before a sensible quantity of nitrous 

 acid developes and then the more gradually will its quantity 

 increase, from which facts the almost necessary inference is that 

 never has quite all nitrite been removed and excluded in pre- 

 paring the acid and that what has been left, though too minute in 

 quantity to aftect the iodide test (which requires 1 in 20 millions, 

 according to Warington), yet multiplies itself by interaction 

 with the hyponitrous acid by forming nitric oxide, which oxidises 

 in the air dissolved in the solution into nitrous acid again. 

 (HNO),+2HNO„=20Ho + 4NO -^ 4HN0,. This aerial oxidation can 

 be demonstrated upon such a solution of hyponitrous acid as 

 Hantzsch and Kaufmann employed in their experiments, which 

 almost at once blued the iodide test ; it being only necessary to 

 leave one portion of it in a deep narrow vessel, such as a test 

 tube half full, and another portion in a shallow basin for ten 

 minutes and then test, when the solution in the basin will be 

 found to liberate more iodine than that in the tube. If in 

 reducing the sodium nitrite, its concentrated solution is shaken, 

 for an hour or two after its main reduction, with excess of the 

 amalgam ; if then this solution is either diluted, acidified cau- 



