AT THE MOMENT OF CHEMICAL CHANGE. 
765 
For the formation of the hyponitric acid from the nitric acid is just as much the 
formation of a new chemical substance as if it were made by the direct action of 
oxygen upon nitric oxide, and is attended with a similar division of the oxygen. But 
this stage of the formation of nitric acid is useless, and not necessary to the concep- 
tion of the change ; for there are other perfectly parallel cases which do not admit of 
such an explanation. 
2. I will take the formation of chloro-sulphuric acid, in the remarkable experiment 
by which Regnault prepared this body*. Olefiant gas, as usually prepared from 
alcohol and sulphuric acid, contains a large quantity of sulphurous acid ; when chlo- 
rine is brought in contact with this mixture of gases, two substances are formed, 
chloro-sulphuric acid, SO2CI, and the Dutchman’s liquid, C4 H4 Clg. Upon sulphu- 
rous acid alone (in the circumstances under which the experiment is made) chlorine 
has no action whatever, nor, according to Regnault, upon olefiant gas, when both 
gases are dry, and only in diffused daylight. The formation, therefore, of this body 
is due to the polar division of the chlorine, just as the formation of sulphuric acid to 
the polar division of the oxygen ; the olefiant gas being to the chlorine in the same 
relation as the nitric oxide to the oxygen in the other experiments, so that we may 
conceive the change to take place thus — 
+ — + — 
C2 H2 ClCl SO,,=C2 H2 Cl+ci so.. 
This example is not open to those objections wdiich, from the formation of the oxides 
of nitrogen, might be raised to the other instance, for here the combinations mutually 
determine each other. With water, the chloro-sulphuric acid decomposes with the 
formation of sulphuric and hydrochloric acids ; but through this experiment we can 
distinctly trace back the cause of the formation of the sulphuric acid, in this, as in 
the more usual mode of its formation, to the polarization of the element ; and on 
considering attentively the mode of the formation of chemical substances, it may be 
seen that the formation of a large class of compounds, among which are the oxides 
of chlorine and iodine, is ever preceded by a similar fact. 
3 . It is well known that when a mixture of hydrogen and any oxide of nitrogeii'i' is 
passed over heated spongy platinum, the oxide of nitrogen is decomposed and am- 
monia and water formed. Were the hydrogen a compound substance, it would be 
thought that the simultaneous formation of these substances was sufficiently explained, 
by saying that it was a case of double decomposition, and it is indeed the same phe- 
nomenon ; thus — 
H — + — 
NO3 H3 Il 3 = 3 HO+NH 3 , 
^ j 
the hydrogen being nascent" from itself. 
* Annales de Chimie, 2nd Series, Ixix. p. 170, and Ixxi. p. 445. 
t See Kuhlmann, Liebig’s Annalen, vol. xxix. p. 286. 
