NITROUS ACIDS. 453 



the air, the quantity of nitric oxide should of course be increased, that 

 it may be present in excess. 



(g.) The processs of Davy. Nitric oxide gas being largely and 

 readily absorbable by the green sulphate, and the green muriate 

 (proto,) of iron, in that condition will attract powerfully the oxygen 

 of the air. 



The nitric oxide which is to be used, should be previously agita- 

 ted in a tube, with one of these solutions, in order to determine 

 whether there is nitrogen mixed with it. A strong watery solu- 

 tion of one of the salts just named, the acid being also saturated with 

 the oxide of iron, is next to be fully impregnated with the ni- 

 tric oxide ; it should be kept in small divided portions in close vials, 

 and applied as it is wanted, in Dr. Hope's Eudiometer, or in some 

 other adequate instrument. 



The protosulphate of iron is preferred, but the solution is liable to 

 spontaneous decomposition, the protoxide of iron attracting oxygen, 

 both from the water and the nitric oxide, and the nitrogen of the lat- 

 ter, combining with the hydrogen of the former, ammonia is gener- 

 ated. Gas is said also to be emitted. See Davy's researches. 



Dr. Hare remarks, " as nitric oxide consists of a volume of nitro- 

 gen and a volume of oxygen uncondensed, to convert it into nitrous 

 acid which consists of a volume of nitrogen, and two volumes of ox- 

 ygen, would require one volume of oxygen. Of course, if nitrous 

 acid be the product, one third of the deficit produced, would be 

 the quantity of atomspheric oxygen present. This would be too 

 much to correspond with the formula of Gay-Lussac." 



" Supposing hyponitrous acid produced, only half as much oxygen 

 would be required, as is necessary to produce nitrous acid ; so that 

 instead of the two volumes of nitric oxide taking one volume, they 

 would take only a half volume. The ratio of J in 2.j, is the same 

 as 1 in 5, or one fifth, which is too little for Gay-Lussac's rule." 



" The formula recommended by Dr. Thomson, agreeably to which, 

 J of the deficit is to be ascribed to oxygen gas, is perfectly consist- 

 ent with the theory of volumes, and much more consonant with the 

 results of my experiments, than that recommended by the celebrated 

 author of that admirable theory."* 



* " The late Professor Dana ingeniously reconciled Gay-Lussac's statement, with 

 the theory of volumes, by suggesting that a half volume of oxygen may take one 

 volume of the nitric oxide, and another half volume of oxygen, two volumes. 

 Vol. Vol. 



oxygen takes 1 oxide and forms nitrous acid. 



& oxygen 2 oxide and forms hyponitrous acid. 



Deficit due to oxygen is as 1 to 3 



This result is evidently dependent upon the contingencies, which may prevent 

 nitrous acid from being the predominant product." 



