ANNALS 



OF 



PHILOSOPHY. 



OCTOBER, 1820. 



Article I. 

 On the Specific Gravity of Gases. By T. Thomson, M.D, F.R.S. 



(Concluded from p. 177.) 



IN the preceding part of this essay, I have endeavoured to esta- 

 bhsh the exact specific gravities of the four simple gases, 

 chlorine, oxygen, azote, and hydrogen, and likewise of the 

 gaseous compounds) which they form with each other. As 

 these specific gravities constitute the true foundation of the 

 atomic theory, all the weights of the more compound bodies 

 being connected with them, and depending on them, I consi- 

 dered it worth while to be at every pains both experimentally and 

 theoretically to arrive at the truth ; and I entertain considerable 

 hopes that I have approached very near absolute precision, if I 

 have not altogether reached it. Hydrogen is the lightest of the 

 gases ; its specific gravity is 0"0694, if we reckon that of com- 

 mon air 1-0000. 



Azote is 14 times heavier than hydrogen, or 0-0694 x 14=0-9722 

 Oxygenic 0-0694 x 16=1-1111 



Chlorine36 0-0694x36=2-5000 



If we reckon the specific gravity of oxygen, unity, as is most 

 convenient for the purpose of the atomic theory, then the specific 

 gravities of these four gases will be as follows : 



Oxygen 1-000 



Hydrogen 0-0625 or ^th of I'OOOO 



Vol. XV J. N<^ IV. Q 



