ALCOHOLIC PREPARATIONS OF THE PHARMACOPCEIA, 49 
have been made by Pharmaceutists, of the proneness to 
decomposition of the compound decoction of aloes, and they 
have suggested remedies for its prevention ; but none have 
pointed out the general nature of the process of decay, 
which differs somewhat from the tinctures from carbonate 
of potash being used in its fabrication. 
If the decoction is examined when first prepared, after 
having been sufficiently boiled, it will be found that the 
carbonate of potash has been decomposed by the resinous 
acids of the myrrh and aloes. On the addition of acetic 
acid no carbonic acid will be evolved, but the resinous 
matter which is in combination with the potash, forming 
compounds analogous to the soaps, will be precipitated, 
and may be re-dissolved by more of the alkali or alcohol. 
When the acetous fermentation has sufficiently advanced 
in the decoction, the alkali will be found in combination 
with acetic acid, which acid has precipitated the resinous 
acids from the base. Crystals of acetate of potash may be 
obtained by evaporating the clear portion of the decoction. 
The resinous matter may be separated from the precipitate 
by the action of a solution of carbonate of potash. 
From the above statement may be gathered answers to 
the questions which have been so often asked, as to whether 
compound decoction of aloes ought to be clear or opaque, 
and in what condition it is proper to use it. Compound 
decoction of aloes, fluid extracts, and all other analogous 
aqueous solutions of vegetable substances, when the spirit 
is added which is used to preserve them, will precipitate a 
portion of the proximate principles held in solution, because 
they are less soluble, or quite insoluble in such a mixture 
of water and alcohol. This precipitation does not fre- 
quently occur at once, from the circumstance that the spirit 
is added to the solution before it is cooled down to that 
temperature at which the principles become insoluble in 
the mixture. It is therefore prudent not to add the spirit 
VOL. XIV. 5 
