" The first runnings were very acid, and smelt pungent, 

 being nitrous acid much phlogisticated ; what came next 

 had no sensible taste or smell ; but the last runnings were 

 very acid, and consisted of nitrous acid not phlogisticated " 

 (A.C.R. III. n). 



Similar mixtures of nitric and nitrous acids were invariably 

 obtained, until Gay-Lussac in 1816 succeeded in obtaining 

 first one acid and then the other as the sole product of the 

 admixture of the gases, and gave the correct limiting 

 proportions as follows : 



Oxygen : nitric oxide = 100 : 133. Product, nitric add. 

 Oxygen : nitric oxide =* 100 : 400. Product, nitrous acid. 



Gay-Lussac in his paper "On the Combinations of Azote 

 with Oxygen " writes : 



" I come now to the combinations of nitrous gas with 

 oxygen : they seem to vary with the slightest change in 

 the conditions-; but I shall prove that there are three 

 distinct combinations which, by their mixing, can explain all 

 those which are not in definite proportions." 



" When nitrous gas and oxygen are mixed, the absorption 

 varies according to the diameter of the tube, the rapidity of 

 mixing, and the order in which the gases are introduced 

 into the tube. Wishing to work over mercury, with water 

 to absorb the acid, but fearing that the mercury would be 

 attacked, I added potash to the water, and thus obtained 

 constant absorptions, independent of the conditions I have 

 just mentioned. I made a great many experiments, and 

 concluded that 100 parts of oxygen absorb 400 of nitrous 

 gas : provided that the solutions of potash are strong, the 

 absorptions are almost all comprised between 495 and 500, 

 and are rarely below 490. This combination of oxygen 

 and nitrous gas, which had not been distinguished, so far as 

 I know, and which I will call provisionally pernitrous add, 1 

 cannot be obtained free ; as soon as one saturates the 

 potash with an acid, nitrous gas is liberated, and ordinary 



] Now called nitrous acid. 



