322 Dr, Thomson on [May, 



Gay-Lussac, in a paper published in an early volume of the 

 Annales de Chimie et de Physique, has given very strong 

 reasons for concluding that the composition of these nve com- 

 pounds is as follows : ' 



Azote. Oxygen. 



Protoxide of azote 100 volumes + 50 volumes 



Deutoxide of azote. 100 +100 



Hyponitrous acid 100 + 150 



Nitrous acid 100 +200 



Nitric acid .« .^I 4-> f^', .. 100 +^250 



As far as I know, these proportions of Gay-Lussac have been 

 adopted by the whole chemical world, with the exception of Mr. 

 Dalton. My object in this paper is to show that the present 

 state of our knowledge leaves no doubt whatever that Gay- 

 Lussac's proportions are accurate, and that Mr. Dalton has 

 misled himself somehow or other. 



1. I take it for granted that the specific gravity of oxygen 

 and azotic gases are as follows : 



Oxygen 1*1111 



Azotic 0-9722 



For the proofs of these specific gravities, I refer tlie reader to 

 the Annals of Philosopfii/, xvi. 163» 



2. I have demonstrated (ibid. p. 171) that the specific gravity 

 of protoxide of azote is 1*5277. 



Now we have 1 volume of azotic gas = 0-9722 

 4- volume of oxygen gas = 0*5555 



1-5277 



Thus when a volume of azotic gas is united to half a volume 

 of oxygen, and the two condensed into one volume, a gas is 

 formed which possesses exactly the specific gravity of protoxide 

 of azote. Hence we are entitled to conclude, that protoxide of 

 azote is a compound of one volume azotic + half a volume of oxy- 

 gen gas condensed into one volume. That this is its true com- 

 position is obvious from the following experiment, which I have 

 often made, and which very nearly agrees with the results given 

 long ago by Davy in his Researches. 



Mix together 100 volumes of protoxide of azote and 100 

 volumes of hydrogen gas. Pass an electrical spark through the 

 mixture ; detonation takes place, the whole hydrogen gas 

 disappears, the residual g|is measures exactly 100 volumes, and 

 is pure azotic gas. Thus we see that 100 volumes of protoxide 

 of azote contain exactly 100 volumes of azotic gas. The 100 

 volumes of hydrogen gas must have been converted into water, 

 and for this conversion they must have united with 50 volumes 



