RESEARCHES UPON SALICIN. 
139 
licin by a solution of bichromate of potassa and sulphuric acid, 
all the elements of the reaction are dissolved in the same li- 
quid, so that in proportion as the chromate of potassa is attack- 
ed, it yields potassa and oxide of chromium, which, in the quan- 
tities indicated, is in amount more than sufficient to neutralise 
the sulphuric acid. Hence, there is formed sulphate of potassa 
and sulphate of chromium, which cannot exercise any action 
upon the organic matters — and the oxygen, in a nascent state, 
can be regarded as the sole element concerned in the reaction. 
On the contrary, in the case where salicin is oxidated under 
the influence of metallic peroxides and sulphuric acid, we may 
conceive, that in consequence of the insolubility of the perox- 
ides used, the reaction cannot be, so to speak, instantaneous, 
and the salicin is submitted, during the whole operation, to 
the simultaneous action of nascent oxygen and a free acid, 
which, as I shall have occasion to show, converts it into sali- 
retin and sugar. The products of the decomposition of salicin 
becoming, in their turn, oxidated, give rise to carbonic and for- 
mic acids. Thus, we may explain this difference, by admit- 
ting that in the first case it is the salicin which is oxidated 
and in the other the oxygen acts upon the salicin and the sugar. 
The following are the experiments upon which I depend to 
sustain this conclusion: — 1. The action which the free acids 
have upon salicin. 2. I am convinced that saliretin does not 
produce the least trace of hyduret of salicyle when treated by 
a solution of bichromate of potassa and sulphuric acid. 3. If 
we distil a mixture of salicin, bichromate of potassa, and sul- 
phuric acid, as if to prepare the hyduret of salicyle, with the 
precaution to use more acid than is necessary to form neutral 
salts with the products of the decomposition of the bichromate, 
we hardly obtain any traces of hyduret of salicyle, and some- 
times none at all; at the same time we may perceive the sali- 
retin produced swimming on the liquid. From this period 
it is impossible to obtain the least quantity of product. 
The hyduret of salicyle, as its name indicates, is such in 
composition as to be considered as a combination of one equi- 
valent of salicyle with one equivalent of hydrogen. The com- 
