1817.) Azote and Oxygen. 189 
such peculiarly distinguishing features of chemical compounds. I 
shall, therefore, dismiss the subject of atmospherical air, and pro- 
ceed to the acknowledged compounds of azote and oxygen. 
It may be proper to state here that the object I have in view is an 
inquiry into the proportions in which the two elements, azote and 
oxygen, are found united in the different compounds, rather than 
to exhibit the physical properties of those compounds, most of 
which are copiously detailed in elementary books, and to which I 
have little new to add. 
Four compounds of azote and oxygen have been long known and 
recognized by chemists, viz. nitrous omide, nitrous gas, nitrous 
acid, and nitric acid: to these I attempted, in 1808, to add an- 
other, which I denominated owynitric acid. Since that time addi- 
tional labour has been bestowed on these compounds, by Gay- 
Lussac, published in the second volume of the Mem. d’Arcueil, 
1809; by Davy, published in 1812; again by Gay-Lussac in the 
Ann. de Chim. 1816; and my own further experience since the 
publication of the second part of my Chemistry in 1810, which 
has not yet been published. On these I shall now remark according 
to the order of time. 
In the year 1808 Gay-Lussac suggested a new idea on the com- 
bination of gaseous bodies, viz. that one measure or volume of one 
gas combines with one of another, or with two, three, &c. or some 
small whole number; an idea evidently agreeing with the atomic 
system in regard to a body’s combining with multiples of another, 
but having no connexion with it in regard to the relation of the 
original two volumes. ‘This idea, it was expected, would derive 
support from the multifarious gaseous compounds of azote and 
oxygen. Those of nitrous gas and oxygen were, at first view, some- 
what averse to the new theory; for it had been proved, in the 
opinion of some, that oxygen combines with nitrous gas in the pro- 
portion of one volume of the former to 1°3 nearly of the latter as a 
minimum, and to 3°6 volumes as a maximum, and further that 
there was no very definite or marked intermediate point which could 
be held as striking or peculiar ; in short, that one volume of oxygen 
might be combined with any intermediate proportion we pleased of 
nitrous gas between 1°3 and 3°6; but that there were limits not to 
be exceeded by any known means. A very timely discovery of a 
new eudiometer by Gay-Lussac completely removed these difficul- 
ties, and most admirably supported his hypothesis, By means of it 
he demonstrated that one measure of oxygen always combines with 
two of nitrous gas, and in no case with less, when the oxygen is 
in excess, and forms nitric acid; and combines with three measures 
of nitrous gas, and in no case with more, when this last is in 
excess, and forms nitrous acid. These conclusions, if true, would 
have annulled the multiplied labours of all his predecessors in this 
department of science; but the experiments on which they are 
founded have not succeeded with any one else, and have recently 
