278 Experiments on the Nature of [Oct. 



definite proportions follows as a necessary consequence, has 

 stated (vol. ii. p. 329), that the smallest quantity of nitrous gas, 

 which in his experiments was condensed by 100 parts in volume 

 of oxygen gas, was always 130. If we convert these volumes 

 into weights we obtain nearly 73*5 oxygen and 26' 5 azote. 

 When I compared this determination with the results of my 

 analyses of the nitrates, I found, to my great surprise, that they 

 accorded much better with it than with the determination of 

 Gay-Lussac, though the difference in the weights that ought to 

 be obtained in the analysis of the nitrates, nitrate of ammonia 

 for example, according to the one or the other of these deter- 

 minations, was so little, that it was impossible to decide by ex- 

 periment which of the two was the most just. 



During my residence in London last summer, Sir Humphry 

 Davy informed me that he had found, by experiments made 

 with the greatest care, that nitric acid is composed in volume of 

 100 parts of azote and 250 of oxygen; that is to say, of 26*5 

 parts, by weight, of azote, and 73'5 of oxygen: for when 

 nitrate of ammonia is distilled in a moderate heat, it is com- 

 pletely changed into nitrous oxide gas and water, without any 

 trace of azotic gas. In the Elements of Chemistry published 

 soon after by this illustrious chemist he has represented nitric 

 acid as a compound of one proportion of azote and five of 

 oxygen. It follows that in the neutral nitrates the acid saturates 

 a quantity of base of which the oxygen is ^th of that of the 

 acid, supposing azote to be the radicle of this acid. As Davy 

 has not admitted the result of the calculations which I have 

 made on the composition of azote, he considers this last sub- 

 stance as an element, and of course he makes no inquiry about 

 the sixth portion of oxygen which ought to exist in the azote. 

 The only experiments of mine which did not agree with the 

 determination of this celebrated chemist were the analyses of 

 the subnitrates and subnitrites of lead at a maximum. I deter- 

 mined, therefore, to repeat them ; and I shall now state the 

 result which I obtained. 



The analysis of the subnitrate of lead at a maximum (men- 

 tioned in my treatise on the composition of the subsalts) being 

 very simple, and very easy to be made with precision, I had no 

 reason to doubt its exactness. It was more probable that I had 

 committed some error in the method of procuring the salt. I 

 might have obtained a mixture of hydrate of lead and subnitrate 

 of lead, or a mixture of two different subnitrates of lead. I 

 resolved, therefore, to examine the precipitates produced in a 

 solution of nitrate of lead by different quantities of ammonia. 



Subnitrate of Lead at a Maximum. — The precipitate obtained 

 by pouring aii excess of ammonia iuto a solution of nitrate of 

 lead was digested for 24 hours in concentrated and caustic nin- 



