ON THE VOLATILE OIL OP BETULA LENTA, ETC. 249 
Gaultheric acid. — This acid is obtained by dissolving 
gaultherin in baryta water, boiling the solution for a short 
time, and afterwards passing a current of carbonic acid 
through the liquid until all the free baryta is removed, and 
filtering. A neutral solution of gaultherate of baryta is 
then obtained, from which the gaultheric acid may be iso- 
lated by cautiously adding dilute sulphuric acid as long as 
a precipitate is produced. The filtered liquid acts strongly 
acid on litmus, and does not precipitate baryta water. By 
evaporation it attains a thick syrupy consistence, and dries 
into a gum-like mass. In this form it is impure. By boil- 
ing it with carbonate of lead until saturated, filtering the 
solution, and then precipitating the lead with hydrosulphuric 
acid, a solution is obtained containing the acid in a much 
purer state, which by evaporation yields it in a nearly color- 
less mass, with some evidence of crystallization. 
Gaultheric acid is soluble in water and alcohol, but is only 
slightly taken up by ether. It saturates acids, forming neu- 
tral salts which do not crystallize. 
By distilling it with dilute sulphuric acid, oil of Gaultheria 
is obtained, and nitric acid appears to act on it like gaul- 
therin. 
The substance existing in the residue of the bark, after 
exhaustion by alcohol, and which reacts with gaultherin to 
produce the volatile oil, has not been isolated. It is inso- 
luble in water, as by long maceration in that fluid it is not 
removed or changed. The temperature of ebullition entire- 
ly destroys its power of acting on gaultherin, which proves 
its analogy to synaptase. Maceration in solution of potassa, 
sp. gr. 1.05, also destroys its power. The impossibility of 
finding a menstruum capable of dissolving this principle, has 
prevented a further examination of its properties. 
In the foregoing observations, some interesting facts have 
been elicited. The existence of a chemical compound of so 
extraordinary a nature as the salicylate of methylene in a 
