1821.] the Comhinations of Azote and Oxygen. 325 



of which is 0-9 inch. This tube is shut at one end and open at 

 the other, and being filled with water is placed inverted on the 

 shelf of the water trough. A hundred volumes of deutoxide of 

 azote are let up to the common air. The mixture becomes yel- 

 low, and diminishes rapidly in volume. I allow the tube to 

 stand untouched till the gas has become clear, and till it ceases 

 sensibly to diminish in bulk. I then introduce the residual gas 

 into a graduated tube, and measure its volume. The average 

 residue, when the experiment is made in this way, is 137 

 volumes. The following table exhibits the residual volume in 

 six successive experiments, the original volume of the two gases 

 being 200. 



Volumes. 



136 

 137 

 137 

 138 

 136 

 137 



Mean .... 136*8 



Thus it appears that when the experiment is made in this way^ 

 the gas which disappears, and which of course must have been 

 converted into an acid and absorbed by the water, amounts to 

 63 volumes. Now 21 of these volumes must have been the 

 oxygen contained in the 100 volumes of common air, and the 

 remaining 42 volumes must have been deutoxide of azote ; but 

 42 is just double 21. Thus we see that when the experiment is 

 made in this way, one volume of oxygen combines with two 

 volumes of deutoxide of azote. This is the same thing as 100 

 volumes of oxygen and 200 volumes of deutoxide of azote ; but 

 200 volumes of deutoxide of azote are composed of 



100 volumes oxygen, 

 100 volumes azotic gas, 



consequently the acid formed in this case is a compound of 100 

 volumes of azotic and 200 volumes of oxygen gas. It is, there- 

 fore, the acid known by the name of nitrous acid, Dulong has 

 shown that this is the acid which is obtained when nitrate of 

 lead is exposed to heat in a retort ; while the receiver is sur- 

 rounded with a mixture of snow and salt. It is an acid of a 

 pale-yellow colour, and seems to undergo decomposition when 

 united to the bases. From Dulong's experiments, it appears to 

 contain no water. Indeed nitrate of lead, when properly dried> 

 is free from water. 



5. I have not yet hit upon a method of uniting 100 volumes of 

 oxygen with 133 volumes of deutoxide of azote. Davy first 

 showed, that if we unite these two gases in these proportions^ 



