ON ALCOHOLIC TINCTURES. 
27 
tained in the evaporated tincture: then, the following pro- 
portion 26-14: 0*94 : : 75 =x gives the total weight of the 
matters the whole of the alcohol has dissolved: x=2gr. -69 
of extract. 
All these experiments were made with the same care. I 
always employed the same substance for each series of ex- 
periments, and for that purpose I prepared powders of each 
in sufficient quantity for all the operations. The macera- 
tion lasted fifteen days in each case, and to avoid any loss 
of alcohol during the filtration, the receiving vessel was 
covered with a sheet of paper fixed to its edge, having in its 
centre a hole just large enough to allow the tube of the 
funnel to pass through : the latter was also covered with a 
sheet of paper kept in its place by a plate of glass. 
As to the means of determining the proper strength of 
the alcohol, it was thought proper to vary it according to 
the nature of the substances to be experimented on. 
When the active principles contained in those substances 
were clearly defined and characterised, I ascertained their 
quanities ; this I was able to do in the case of barks, mix 
vomica and jalap. 
These quantities were ascertained in the following man- 
ner: for bark and nux vomica the tincture was evaporated 
in a sand-bath, and the extract obtained was treated with aci- 
dulated water, the filtered liquor was precipitated by means 
of subacetate of lead, to remove feverish matters from the 
alkaloi'd, and then the excess of lead having been separated 
by sulphuretted hydrogen, the alkaloids were precipitated 
by means of a solution of pure tannin; it was therefore 
while in the state of tannatea that the quantities of the alka- 
loids were ascertained. 
For jalap, I extracted the resin of a given quantity of the 
tincture. 
But if, in the case of these substances, the management 
was easy, it is not the same for the greater number, in 
which the active principles are ill defined, and possess no 
characteristic chemical properties. How, for example, in 
