78 PROVOSTAYE ON THE ACTION OF 
were prepared separately, each perfectly dry. The sulphurous 
acid was first poured on the anhydrous sulphuric acid in the 
bend C; and afterwards the hyponitric acid was introduced into 
KE, as in former experiments, closing the extremities with a lamp, 
and mixing the liquids. The combination was effected almost 
immediately, and without the smallest apparent decomposition. 
The green liquid was now no longer produced. The substance 
thus obtained fused at 215° cent. (419° Fahr.), and presented 
all the characters of the substance obtained by the action of dry 
sulphurous and hyponitric acids. 
In the second place, on comparing the crystals of the pure 
anhydrous substance with those of anhydrous sulphuric acid, 
they are found to be absolutely similar: the same silky tufts, 
the same elongated needles. Viewed through a microscope, it 
would be impossible to distinguish one from the other, if con- 
tained in the same tube. This apparent isomorphism seems to 
establish clearly that the new substance ought to be regarded as 
containing anhydrous sulphuric acid, in which one equivalent 
of oxygen is replaced by one equivalent of hyponitric acid. 
In this hypothesis it is easy to explain the property which is 
possessed by sulphuric acid, of dissolving this substance in all 
proportions, and always producing (within very extensive limits) 
solid crystallizable compounds ; the reason of which would not 
be apparent on any contrary supposition *. I am not aware 
whether satisfactory experiments have been performed to de- 
monstrate the existence of a di-hydrated sulphuric acid (H O 
+280), which is admitted by some chemists. If there have 
not, can it not be presumed that anhydrous sulphuric acid 
likewise is dissolved in several proportions, and forms several 
crystallizable compounds with oil of vitriol, that is, with sulphuric 
acid containing one proportion of water ? 
Nothing is now easier than to explain the discordant results 
which have hitherto been obtained by distinguished chemists. 
It is evident that they have analysed different substances; re- 
garded as identical merely for this reason,—that they crystallize. 
This entirely insufficient character ought to be replaced by one 
much more satisfactory in this instance,—namely, the tempera- 
ture of the point at which they fuse. 
The preceding researches throw great light on the reactions 
* It is proper to remark that the formula of the crystals examined by Dr. 
Henry may be expressed thus: S O:, NO, + HO + 4(S 0,0, HO); or, 
adopting six proportions of water, SO:,N 0, + 50,0 +3 (SO, 2H 0). 
