192 On the Chemical Compounds of [Marcu, 
nished Dr. Henry with a table of nitric acid, which was printed in 
the seventh edition of his Chemistry last year (1815). 
Having fallen into an error, along with my cotemporaries, in re- 
gard to the constitution of nitrie acid, it is proper to state what I 
have to allege by way of exculpation, especially as 1 profess to 
publish as little as possible but what I can support on my own ex- 
perience. : 6. 
It appeared to be well established by the concurring experiments 
of Kirwan, Richter, and Davy, that the nitrate of potash is con- 
stituted of 47 or 48 acid and 52 or 53 potash. My own former 
experiments did not oppose this conclusion; though it now appears 
that numbers the reverse of the above are more approximate to the 
truth. I had previously ascertained the relative weight of the atom 
of potash to be 42, from a comparison of several salts; and hence 
that of nitric acid was deduced to be 38. Now one atom of azote 
and two of oxygen making just 19, I concluded that two such com- 
pounds must form the atom of nitric acid united to one of potash, 
as there did not appear any other way of forming a compound of 38 
out of the elements of azote and oxygen. What contributed mate- 
rially to confirm this conclusion was the near coincidence of the 
proportion of azote and oxygen with that determined by the cele- 
brated experiments of Mr. Cavendish, as well as its agreement with 
the results obtained by the electrification of nitrous gas. 
Knowing that nitric acid, if so constituted, must be formed of 
one measure oxygen and 1-8 nitrous gas, I was well aware from 
experiment that an acid with a greater proportion of oxygen was 
attainable, and hence inferred the existence of oxynitric acid, as 
well as nitrous acid, which I formed by combining one measure 
oxygen with 3°6 nitrous gas, or twice the volume necessary for 
nitric acid. The ideas of these compounds are rendered easily in- 
telligible by the symbols invented for the purpose, and delineated 
in the fifth plate of my Chemistry. 
Subsequent experiments having disproved the accuracy of the 
fundamental fact on which this theory of nitric acid was formed, it 
became necessary to modify it accordingly. It now appears, from 
the best experiments we have, that nitre is formed of 52 parts acid 
and 48 potash nearly, the ratio of which is that of 45 to 42 nearly. 
Hence the atom of nitric acid contains two atoms of azote and five 
of oxygen, or two of nitrous gas and three of oxygen ; and it may 
be formed by uniting one measure of oxygen with 1°2 of nitrous 
gas, which appears to be the minimum. Or 100 parts of azote by 
weight take 350 of oxygen to form nitric acid. ‘The compound 
which I formerly denominated nitric acid, if it exist, which seems 
probable, may be denominated nitrous acid gas, and what I called 
nitrous acid is the pernitrous acid of Gay-Lussac, or, as I should 
rather call it, sulnitrous acid, admitting the existence of the other 
compound. 
If this explanation be admitted, it is evident we must hencefor- 
ward consider the compound formed by electrifying a mixture of 
