On the Preservation of Medicines. 275 
dried and kept in glass vessels, and not in too large quanti- 
ties together, they will remain unimpaired. The alkaline lo- 
zenges of soda, which are white when fresh made, should be 
kept as much as possible from the contact of air, or they will 
moisten and become yellow ; this most commonly arises from 
the employment of a simple carbonate of soda. 
Extracts are liable by keeping, to be covered with mould 
which is by some considered unavoidable ; some assert that an 
extract loses none of its activity by mouldiness, and hence take 
no measures to prevent it ; others with the view to oppose it, 
protect the upper surface of extracts by paper saturated with 
spirit of wine, which is but a temporary shield ; or mix a por- 
tion of olive oil with them, during their preparation, which 
answers this purpose very well, and serves also to keep them 
of a proper consistence. The last may, however, be deemed 
objectionable, from their want of ready solubility. 
The common method of covering extracts is by means 
of bladder or sheep skin. This does not prevent their becom- 
ing mouldy, nor does it preserve their consistence, for the 
extracts are sometimes found so hard as to be with difficulty 
separated from the pots which contain them, when it is ne- 
cessary to make them up again, by means of a water bath. 
When the alcoholic extracts of colocynth, jalap, and nux 
vomica, become hard, they may be rendered of a good con- 
sistence, without any trouble, by dropping some alcohol upon 
their surface, which gradually incorporates itself with them. 
Extracts should be kept in porcelain pots, with covers of the 
same material. A small one only should be kept for officinal 
use, and the remainder put away, after the manner recom- 
mended by Mr. M,, in double vessels, in the first of which 
are to be put now and then a few drops of water. The im- 
ported extracts, principally German and French, are the best, 
and in greater demand, from physicians being able to depend 
upon their efficiency; and are much superior to those of this 
country, which are chiefly obtained from the Shakers. These 
last extracts from being entrusted to persons, ignorant of the 
first principles of chemistry, are often negligently prepared* 
