140 
CHEMICAL PHENOMENA OP DIGESTION- 
gave no acid reaction. As a counter-proof we distilled 
water, very faintly acidulated with vinegar: the first pro- 
ducts of the distillation manifested an acid reaction. Gastric 
juice, to which we added a trace of acetic acid and even 
acetate of soda, behaved in the same manner by distillation. 
Having saturated gastric juice with carbonate of soda, then 
evaporated the solution to dryness and treated the residue 
with arsenious acid, we did not recognize the odour of .ox- 
ide of cacodyle, which is, as is well known, so characteristic 
of acetic acid. From these experiments it seems to us 
proved that gastric juice does not contain any free acetic 
acid, neither does it any of the acetate. 
Upon reflecting that the first products by distillation of 
gastric juice never give an acid liquid, we were tempted to 
avail ourselves of this fact, to reject also the presence of 
free hydrochloric acid, because according to the received 
notions, this acid which is volatile should have passed over 
in the first instance. We should, however, have committed 
an error, as will be seen by the following experiment: In 
fact, if you slightly acidulate water with hydrochloric acid 
and distill it, you will remark that nothing passes at first by 
distillation but pure water, whilst the acid which concen- 
trates in the last products is only disengaged at the close of 
the operation. This unlooked for circumstance determined 
us upon distilling anew the pure gastric juice, and pushing 
the distillation to dryness. Here are the results : At first 
and nearly throughout the experiment, nothing passed but 
a limpid neutral liquid, affording no precipitate with nitrate 
of silver ; afterwards nearly four-fifths of the juice having 
evaporated, a liquid sensibly acid is distilled, but furnishing 
no precipitate with the salts of silver. Lastly, near the ter- 
mination, and when there remains but a few drops of gas- 
tric juice to evaporate, the liquid acid which is produced 
yields with salts of silver a precipitate so decided as not to 
be taken up by concentrated nitric acid. Beyond doubt 
this last product is hydrochloric acid, but it remains to be 
