HYDROFLUORIC ACID. 429 



no special consideration to this acid. It is sufficient to remind 

 our readers, that, according to our experiments,* lactic acid can be 

 replaced by no other acid, except hydrochloric acid, in the process 

 of digestion. 



HYDROFLUORIC ACID. 



Brugnatellif believed that he had discovered the existence of 

 this acid in the gastric juice of birds, when he found that pieces of 

 agate and rock-crystal, which he introduced by means of tubes into 

 the stomachs of common fowls and turkeys, were distinctly corroded, 

 and had lost from 12 to 14 grains in weight, on their removal after 

 ten days ; and TreviranusJ also believed that, when the contents of 

 the intestinal canal of fowls were digested in porcelain vessels, the 

 glazing was attacked. 



In reference to the small quantities of this acid which might 

 possibly occur in the gastric and intestinal juices of these animals, 

 it is certainly difficult to demonstrate its absence in an unques- 

 tionable manner ; but as theoretical reasons as well as direct expe- 

 riments are opposed to Brugnatellr's view, we may, at all events, 

 with great probability, assume the non- occurrence of this acid. 

 Tiedemann and Gmelm, digested the gastric juice of a duck for 

 24 hours in a platinum crucible, which was covered with a piece of 

 glass having a coating of wax through which a few lines were drawn ; 

 they could, however, detect no corrosion on the glass. I 

 placed the chyle of a duck which had just been killed, in a 

 platinum crucible, treated the mass with a little sulphuric 

 acid, and covered the crucible with a watch-glass coated with 

 wax except at the centre (the inferior convex part) where its 

 surface was bare and exposed; at the termination of the experi- 

 ment, I could not find the slightest corrosion on the watch-glass. 

 Further, I saturated with potash the fluid obtained by washing the 

 contents of the crop and stomach of two turkeys with water, eva- 

 porated it to dryness and burned the residue ; the ash was then 

 carefully treated with sulphuric acid in a platinum crucible, in the 

 manner already described, but here also no trace of hydrofluoric 

 acid was obtained. 



If these experiments are not sufficiently stringent to overthrow 



* Ber. d. k. sachs. Ges. d. Wiss. z. Leipzig. 1849. 

 t Crell's Ann. 1787- Bd. 1, S. 230. 

 J Biologie. Bd. 4, S. 362. 

 Verdammg. Bd. 2, S. 139. 



