192 Dr. Thomas Thomsons Observations 



fragments of chloride of calcium. The loss of weight sus- 

 tained hy the glass tube containing the oxide of copper, 

 o-ave the quantity of oxygen employed, while the increase 

 of weight in the chloride of calcium tube, gave the quantity 

 of water formed. The result of the experiments was, that 

 water is a compound of 



Oxygen . . 889 or 1 

 Hydrogen . Ill or 0-12486 



A number which does not differ by one-thousandth part 

 from that deduced from the specific gravity of hydrogen 

 gas, as determined by my experiments. The number 0-125 

 being generally adopted in this country, as the true atomic 

 weight of hydrogen, I consider it as needless to enter into 

 the subject more at large, otherwise it would be easy to 

 shew, that the number adopted by Berzelius, differs from 

 mine, by a quantity certainly within the limits of the un- 

 avoidable errors to which such experiments are liable. 



4. Let us now see what the atomic weight of azote must 

 be, determined from the specific gravity of oxygen and 

 azotic gases. I have shown, that the true specific gravity 

 of oxygen gas is 1-1111, and of azotic gas 0-9722. Now* 

 Mill : 0-9722 :: 16 : 14. So that the weight of equal 

 volumes of the two gases are to each other as 16 to 14. 



There are two gaseous compounds of oxygen and azotic 

 gas; namely, nitrous gas, or deutoxide of azote, as it is now 

 commonly called, which is a compound of 1 volume of oxy- 

 gen and 1 volume of azotic gas ; and nitrous oxide or pro- 

 toxide of azote, which is a compound of 2 volumes of azote 

 and one volume of oxygen gas. Nitrous gas is composed 

 by weight of 



Oxygen 1-1111 or 16 or 1 

 Azote 0-9722 or 14 or 0-875 



Nitrous oxide of 



Oxygen 1*1111 or 16 or 1 

 Azote 0-9722 x 2 or 28 or 1-75 



Thus, there are two numbers, which may either represent 

 the atom of azote, according as we consider nitrous gas or 

 nitrous oxide as composed of a single atom of oxygen united 

 to a single atom of azote. Mr. Dalton adopted the first of 

 these numbers, in his original treatise on the atomic theory, 

 in his Philosophy of chemistry, and his view of the subject 





