28 
ON ALCOHOLIC TINCTURES. 
the case of hemlock,, rhubarb, gentian, &c, can we discover 
whether the tincture prepared by means of alcohol at 80°, 
contains a greater proportion of the active principles than 
that prepared with alchol at 56 ? 
Among these substances there are some whose properties 
are contained in a bitter principle, as in the case of rhubarb, 
gentian, and wormwood. For these substances I took two 
determinate quantities, prepared with alcohol of different 
degrees of strength, diluting them with water to discover 
that which required the greatest quantity of this liquid to 
remove the bitterness. Unfortunately there are too many 
substances for which this mode of investigation cannot be 
employed, and this was a difficulty I was unable to over- 
come ; it was only by calculation based on the chemical 
analysis of these substances, that I selected alcohol of a fit- 
ting strength. The only method, in my opinion, of attain- 
ing the desired object in these cases would be to employ 
medically, tinctures prepared with these matters, and alco- 
hol of different degrees of strength. 
The strength of the alcohols I employed were to the 
' number of five, namely, alcohol at 90, 80, 70, 56, 45 per 
cent. 
To make the facts I relate intelligible, I will, in the first 
instance, lay down the following principles, to which I was 
guided by nearly 300 experiments made in this manner. 
1. The different strength of the alcohols recommended 
by the " codex" are not always those which are the best to 
dissolve the active principles contained in the substance em- 
ployed. 
2. The proportion of four parts of alcohol for one of 
the substance, adopted by the codex, is scarcely in any case 
•sufficient to dissolve, entirely, the soluble matters of those 
substances. 
3. The proportion of alcohol necessary completely to ex- 
haust these substances, is five parts of alcohol to one of 
the substance employed. In two or three cases, however, 
four parts of alcohol are sufficient, but it is useful, I think, 
