Fiff. 4. 



174 Dr. Hare on the Cotistritction and Applications of the 



gas, there will be just enough to condense two volumes of ni 

 trie oxide by converting them into nitrous 

 acid. Of course of the eight volumes in 

 the tube, three will disappear and five re- 

 main. Hence the gas after the absorption 

 of the red fumes will occupy tlie same space 

 as the air before the introduction of the ni- 

 tric oxide. The extent of the deviation, 

 from this result, may be measured by intro- 

 ducing hydrogen by means of the sliding- 

 rod gas measure, until the quantity added 

 causes the gas to extend to the next gra- 

 duation. By these means it is easy to as- 

 certain how much the residue differs from 

 five or six volumes. I have always found 

 it rather less than five volumes. 



It is pleasing to observe the perfect co- 

 incidence between the results, whether at- 

 mospheric air be analysed in the volume- 

 scope by explosion with hydrogen, or by 

 its spontaneous reaction with nitric oxide, 

 five volumes of air being in the one case 

 mingled with three of nitric oxide, in the 

 other with a like proportion of hydrogen. 

 I am the more gratified at being enabled to make this state- 

 ment, as the directions given by such eminent chemists as 

 Dalton, Gay-Lussac, Henry, and Thomson, are discordant. 



Gay-Lussac has given a formula, agreeably to which one- 

 fourth of the condensation produced by a mixture of equal parts 

 of atmospheric air and nitric oxide, is to be assumed as the at- 

 mospheric oxygen present. As nitric oxide consists of a vo- 

 lume of nitrogen and a volume of oxygen, uncondcnsed ; to 

 convert it into nitrous acid, which consists of a volume of 

 nitrogen and two volumes of oxygen, 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 

 atmospheric oxygen present' This would be too much to cor- 

 respond with the formula of Gay-Lussac. 



Supposing hypo-nitrous acid produced, only one-half as 

 much oxygen would be required as is necessary to produce 

 nitrous acid ; so that instead of two volumes of nitric oxide 

 taking one volume, they would take only a half volume. The 

 ratio of ^ in 2^ is the same as one in five or j, which is too 

 little for Gay-Lussac's rule. 



The formula recommended by Dr. Thomson, agreeably to 

 which, one- third of the deficit is to be ascribed to oxygen gas, 



