22 ON ALCOHOLIC TINCTURES. 
is proved that the active principle is more soluble ii weak 
alcohol, the preference is given to the latter. In the case 
of substances on the nature of which analysis has not yet 
decided, the strength of the alcohol has been chosen, in a 
manner that is almost empirical, basing it always upon 
analogy. 
Relying upon these facts, the "codex" has adopted alco- 
hol of three different degrees of strength for the preparation 
of tinctures; these degrees are 36°, 32° and 22° of Baume or 
86°, 80° and 56° of the centesimal scale. Alcohol at 86° 
is reserved for substances which are loaded with fat and 
little soluble substances. Alcohol at 80° for substances con- 
taining various resinous principles and volatile oil, and 
lastly, alcohol at 56° for substances of an extractive nature. 
Are these three different degrees of strength which are 
recommended, the most fitted for the preparation of alco- 
holic tinctures ? several isolated experiments have thrown, 
a doubt upon this first point. 
The intention of alcoholic tinctures is also to provide 
practitioners with solutions of a known strength, that they 
may be able to calculate the relative proportion between 
the quantity of the tincture prescribed, and that of the sub- 
stance used in its preparation. 
The extremely varying nature of the vegetable and ani- 
mal substances used in the preparation of these medica- 
ments, cause us to imagine, in the very onset, that the same 
quantity of the vehicle cannot be sufficient to dissolve, en- 
tirely, all the principles contained in each of these sub- 
stances : in that case the proportion of the alcohol ought 
to vary according to the quantity of soluble matters contain- 
ed in the substances employed. But as it is useful that 
practitioners should easily remember these proportions, dif- 
ferent authors all agree to admit but a small number. On 
this account the " codex" prescribes, in most cases, the pro- 
portions of four parts of alcohol for one part of the substance 
employed. 
