45 ALCOHOLIC PREPARATIONS OP THE PHARMACOPCEIA. 
soluble on the addition of a sufficient quantity of spirit to 
supply the place of that decomposed. This circumstance 
shows that a part of the precipitate was caused by the de- 
composition of the alcohol, and a part by the destruction of 
the vegetable principles themselves. When the tinctures 
in this condition were completely exposed to the action of 
/ the atmosphere at a sufficient temperature, the alcohol con- 
tained in them was speedily and entirely converted into 
acetic acid. 
The proof-spirit tinctures most liable to the acetous fer- 
mentation are those which contain those proximate princi- 
ples in solution which are prone, per se, to decay, the 
spirituous menstruum not having sufficient antiseptic power 
to permanently resist their decomposition. The tinctures 
made with rectified spirit are not susceptible of any change 
of a similar character, neither are the tinctures above 
spoken of, when the strength of the spirit is considerably 
increased, arising from the insolubility of some of the proxi- 
mate principles prone to decay in the stronger spirit, as 
well as its antiseptic quality. 
That the acetous fermentation is induced in the tinctures 
by the presence of bodies in a state of change, acting as a 
ferment, is clear from the fact that a mixture of alcohol and 
water will not ferment without the presence of some such 
body. It is also evident that the vegetable substances held 
originally in solution have been subject to a material 
change by the loss of colour and taste of the tincture, and 
by it containing a precipitate, a portion of which was in- 
soluble in a mixture of alcohol and water. 
Some of the preparations most prone to this change are 
the tinctures of senna, rhubarb, columba, henbane, digitalis, 
bark, hops, aloes, compound tincture of cinnamon, com- 
pound decoction of aloes, concentrated infusions, fluid ex- 
tracts, and all similar preparations, especially those which 
are weaker in spirit than the tinctures. Many complaints 
