330 Analysis of the Labours of the Royal Academy 



of each at its boiling temperature gives, under an equal pressure, 

 the same vohune of vapour ; or in other terms, that the densities 

 of their vapours bear the same relation as those of liquids ta 

 their respective boiling temperatures. 



M. Gav Lussac intends to pursue his experiments, and to pre- 

 sent very soon more comfilete researches upon the dilatation of 

 liquid* and upon their capacity for caloric. 



Among the delicate questions which are at present agitated 

 in chemistry, one of the most important respects the proportions 

 in which the elements unite in forming different combinations. 

 These sorts of researches are subject to great difficulties, be- 

 cause it is not always possible to obtain insulated combinations 

 of gas ; and when it is wished to extract them from the salts of 

 which they make part, they are liable to be decomposed or al- 

 tered by the intermixture of other principles of these salts, or of 

 water which almost always presents itself. It is thus that the 

 remarkable differences between the results of Davy, Dalton, and 

 ■Gay Lussac, respecting the combinations of azote and oxygen, 

 may be explained. 



From experiments presented this year to the Academy by 

 M. Gay Lussac, it appears that nitrous gas cjiitains a volume 

 of azote and an eqr.d volume of oxygen Avithout condensation; 

 that in certain circumstances it presents a combination of a 

 volume of azote with a volume and a half of ox\gen ; and to this 

 M. Gay Lussac has given the name of pernitrous acid {acide 

 pernitreux) : — That ordinary nitrous acid is composed of a 

 vohune of azote with two volumes of oxygen : — lastly, That there 

 is in nitric acid a volume of azote and two volumes and a half 

 of oxygen. 



Among these different varieties of oxides or acids which have 

 azote for their base, he has found one which is obtained from 

 the distillation of the neuter nitrate of lead previously dried. It 

 is a very volatile liquid of an orange colour. M. Gay Lussac 

 regards it as nitrous acid, the elements of which are retained by 

 the action of water which he supposes makes part of it. But 

 M. Dulong has satisfied himself by very exact analyses that it 

 does not contain water ; and he calls it for this reason anhydro- 

 nitrous acid {acide nitreux anhydre). The result obtained by 

 M. Dulong has been confirmed synthetically. A volume of ni- 

 trous gas, and somewhat more than two volumes of oxygen, sub- 

 mitted to an artificial cold of twenty degrees, give that acid, 

 which among other properties changes colour not only by inter- 

 mixture with water, but by heat ; — colourless at 20° below zero, 

 it becomes of an orange hue at 15° above it, and almost red at 

 2S". Four parts of nitrous gas and one part of oxygen gas, con- 

 densed bv cold, have yielded a much more volatile liquid than 



the 



