1820.] Specific Graviti/ of Gases. 171 



by the name of gaseous oxide of azote; and 2, deiiloxide of azote^ 

 the gas which has been so long known by the epithet ?/«V;-OMS^as, 

 a name first imposed upon it by Dr. Priestley. 



I consider it as demonstrated Xh^iX. protoxide of azote i?, a com- 

 pound of half a volume oxygen gas and one volume azotic gas 

 condensed into one volume. Ot course we obtain its specific 

 gravity by adding to the specific gravity of azotic gas half the 

 specific gravity of oxygen gas. 



Specific gravity of azotic gas .... = 0*9722 

 Half specific gravity of oxygen gas = 0-5555 



1-5277 



So that the specific gravity of protoxide of azote by theory comes 

 out 1-5278. A quantity of this gas was prepared in the usual 

 manner from nitrate of ammonia, and great care was taken to 

 exclude every portion of common air. Three different trials were 

 made on the specific gravity of this gas. The results were as 

 follows : 



By first trial 1-5269 



By second trial 1-5269 



By third trial 1-5269 



All these results agree perfectly with each other. They give 

 the specific gravity of the gas not quite so much as , ^'pp th part 

 less than the theoretical result. Now this small difference being 

 within the limits of unavoidable error, 1 consider myself entitled 

 to conclude from the above experiments that the true specific 

 gravity of protoxide of azote is 1-5278, as theory indicates. The 

 mixture of rather less than -^t\\ part of the volume of the gas 

 of conmion air would have been sufficient to produce the altera- 

 tion which we found in the specific gravity of our gas. In other 

 words, if the gas which we weighed had been a mixture of 499 

 volumes of protoxide of azote and 1 volume of air, its specific 

 gravity would have been only 1-5269, as we found it, allowing 

 the specific gravity of pure protoxide of azote to be 1-5278. 

 Now 1 am not aware of any good method of detecting so small a 

 quantity of common air in protoxide of azote as this. The only 

 person who attempted to determine the specific gravity of protox- 

 ide of azote before the experiments made in my laboratory above 

 stated, was M.Colin. He obtained 1-5204. His gas was no 

 doubt a mixture of 98*6 volumes of protoxide of azote and 1-4 

 volume of common air ; for such a mixture would have precisely 

 the specific gravity found by M. Colin. 



Gay-Lussac showed long ago. that deutoxide of azote is a 

 compound of one volume of oxygen gas and one volume of azotic 

 gas united without undergoing any condensation whatever; 

 therefore the true specific gravity of this gas is exactly the mean 

 between the specific gravity of oxygen gas and that of azotic 



