1821.] the Combinations of Azote and Ojcy gen, 323? 



of oxygen gas; consequently 100 volumes of protoxide of azote 

 contain exactly 50 volumes of oxygen gas. 



The only difficulty attending this experiment is to procure 

 protoxide of azote in a state of absolute purity. I have fre- 

 quently had it so pure that the error in the results did not 

 amount to so much as half per cent. This I consider as a 

 demonstration that Dalton's proportion of oxygen, which he 

 makes 62 volumes, is excessive. Were this the quantity, 124 

 volumes of hydrogen gas would be requisite instead of lOQ 

 volumes ; and after burning a mixture of 100 volumes of protox* 

 ide of azote and 100 volumes of hydrogen, a portion of protoxide 

 of azote (amounting to rather more than 20 volumes) should 

 remain undecomposed, or 12 volumes of oxygen gas should be 

 found in the residual gas, which, instead of 100 volumes, would 

 amount to 112 volumes. 



If Mr. Dalton will consider these facts, he will, I think, see 

 the necessity of admitting that protoxide of azote is a compound 

 of 100 volumes azotic + 50 volumes oxygen gas condensed 

 into 100 volumes. 



2, That deutoxide of azote is a compound of 100 volumes 

 azotic +100 volumes oxygen gas united together, and consti- 

 tuting 200 volumes, will not admit of doubt, if we attend to its 

 specific gravity, which I have shown to be 1*04166 {Ammls of 

 Philosophy y x vi. 172.) Now this is exactly the mean of the spe- 

 cific gravities of oxygen and azotic gases ; for 



Oxygen = Mill 



Azotic .,..-,-, ==0-9722 



^ ' 2)2-0833 



Mean...... = 1-04166 



1 have not myself made any experiments to determine the 

 quantity of oxygen in deutoxide of azote by combustion ; but 

 the evidence adduced by Gay-Lussac in the second volume of 

 the Memoires d'Arcueil, that this gas is composed of equal 

 volumes of oxygen and azotic gas, is so conclusive as to leave 

 no doubts whatever on my mind of its truth.. 



3. I have attempted to verify Gay-Lussac's experiments, in 

 which he made one volume of oxygen gas unite with four 

 volumes of deutoxide of azote ; but though I have returned to 

 the subject more than once at different periods of the year, I 

 have never been so fortunate as to obtain the same results with 

 that very ingenious philosopher. I have, however, succeeded 

 in hitting upon a method by which this combination can be 

 accomplished at all times with the greatest ease. Indeed I 

 have since found that this method is not new. It was practised 

 by Mr. Cavendish as long ago as 1783, and is minutely described 



x2 



