436 A Comparison of the Old and New Theories (Jun, 
moisture. The crystallized body obtained by this means is a che- 
mical compound of sulphuric acid and nitrous acid, in which the 
latter contains one-third of the oxygen contained in the former 
(= NOt + 480%). It seems, likewise, to contain some water.* 
When this compound acid is gently heated, it melts like fat, but 
crystallizes on cooling. When mixed with a little water, it is de- 
composed, and converted into common sulphuric acid and hydrous 
nitrous acid, and this last liquid, according to the proportion of 
water, is yellow, green, or blue. When so much water is added 
as to render it colourless, the nitrous acid is completely decomposed 
into nitric acid and nitrous gas, just as is the case with common red 
nitric acid. When the compound acid is distilled in a glass retort, 
the nitrous acid is converted (partly by absorbing oxygen, partly by 
giving out nitrous gas) into nitric acid, and we obtain a compound 
of sulphuric and nitric acids, which cannot be decomposed by dis- 
tillation (unless they be previously diluted with water). This com- 
pound acid is heavier than common sulphuric acid, and may be 
obtained of the specific gravity 1°94 or 1°96. It does not crystallize 
when cooled down, and dissolves metals with the evolution of 
nitrous gas. 
We have here an example of two compound acids of sulphurie 
acid, the one with nitrous acid, the other with nitric acid. Hence 
we see that other compound acids exist besides the disputed ones 5 
and have ground to conclude that similar compounds of the other 
acids, namely, muriatic acid, phosphoric acid, fluoric acid, iodine 
with nitrous and nitric acids, must exist, and only require investi- 
gation to be discovered. We perceive, therefore, that the difficulty 
of accounting for the explosion of chloride of azote is not the only 
reason for considering this body as a compound of muriatic acid 
with nitrous or nitric acids. 
We are not entitled to demand of the old doctrine an explanation 
why the acids combine together in the middle, or at least on the 
surface, of water, and then are brought by the water slowly, and 
with difficulty, to the state of hydrous acids, though they have a 
stronger affinity for water than for each other. Neither will'we 
require of the new doctrine to explain why, although the affinity of 
chlorine to hydrogen, and of azote to oxygen, be greater than that 
of oxygen to hydrogen (so that chloride of azote gradually decom- 
poses water at the common temperature, and forms muriatic acid 
and nitric acid), yet these acids are not formed at once, as chloride 
of azote may be obtained in the midst of, or on the surface of, 
water. Wesce that the difficulty of explaining these facts is the 
same, whatever doctrine we embrace. 
Gay-Lussac has very properly stated the difficulty of an explosion 
from mere decomposition, and asks (Gilbert’s Annalen, vol. xlix. 
* A very interesting method of obtaining this compound acid, but not instruc- 
tive with respect to ifs nature, will be found in Dayy’s Elem. of Chem, Phil. 
p. 276 
