1821 J the Comhinations of Azote and Oxygen, 327 



Azote. Oxygen. 



' 100 volumes -f 250 volumes. 



Now this is the very constitution pointed out by Davy and by 

 Gay-Lussac. 



6. About the year 1806, Mr. Dalton pubHshed a set of experi- 

 ments to determine the proportion of the several gases in the 

 atmospliere.* In this paper he remarks, that if 36 volumes of 

 pure deutoxide of azote be introduced into a glass tube about 

 three-tenths of an inch v/ide, and 100 volumes of common air be 

 let up into it, after a few minutes the whole will be reduced to 

 79 or 80 volumes, and will exhibit no signs of either oxygen, or 

 dentoxide of azote. In this case, 21 volumes of oxygen have 

 united with o6 volumes of deutoxide of azote; If the same expe- 

 riment be made in a wide vessel, a common tumbler, for instance, 

 .and if we employ 72 volumes of deutoxide of azote and 100 

 volumes of common air, the residue will be as before, 79 or 80 

 volumes. Thus 21 volumes of oxygen unite with 36 volumes of 

 deutoxide of azote in a narrow tube, and with 36 x 2 = 72 

 volumes. in a wide vessel. This is equivalent to 



Oxygen. Deutoxide of azote. 



100 volumes 4- 171*429 volumes 

 100 -h 342-858 



The diminution of volume in a narrow tube he finds so con- 

 stant that he recommends this mode of experimenting as a good 

 method of detecting the volume of oxygen in a given quantity of 

 gas. Take a given volume of it, and let up into it a given volume 

 of deutoxide of azote. Note the diminution of volume ; 7-19ths 

 of this diminution is the oxygen required ; so that, according to 

 this rule, v/e have only to multiply the diminution of volume by 

 0*3684 ; the product is the volume of oxygen required. 



I have made a great many trials to verify these conclusions of 

 Mr. Dalton. Indeed I adopted his mode of determining the 

 proportion of oxygen in mixed gases by means of deutoxide of 

 azote as soon as I became acquainted with it ; but the want of 

 coincidence between diiferent trials, though made in precisely 

 the same way, led me at last to doubt its precision, and to make 

 a set of experiments in order to investigate what really takes 

 place. I found, in the first place, that the results did not vary 

 sensibly, whether we employed glass tubes of the bore 0*3, 0*4, 

 or 0*5 inch. My mode of proceeding was to put 100 volumes of 

 common air into a graduated tube, and to let up into it 100 

 volumes of deutoxide of azote. After the diminution of volume 

 was at an end, I noted the volume of residual gas. The follow- 

 ing table exhibits the volume of residual gas in six successive 

 experiments made in this way in a tube of 0*5 inch in diameter : 



♦ Phil. Mag. xxiii. 351. 



