dltRUS MEDlCA. 
189 
i-^adily with spirit of wine; for a spirituous exti*act made from lemon 
peel retains its aromatic taste and smell in much greater per* 
fectioii, than an extract prepared in the same manner from orange 
peel. The juice of the lemon is a sharp, grateful acid, analogous 
to that of oranges, from which it only differs in containing more 
citric acid, and less syrup. The simple expressed juice will not 
keep, on account of the syrup, extractive, mucilage and water; 
which cause it to ferment, and hence many modes have been recom- 
mended for preserving it for use. In the navy, it has been mixed 
with a fifth or a sixth part of brandy, or rum, and in this way has 
been kept for more than two years without undergoing any change,* 
biitthis is not pure lemon juice. Perhaps the best mode of pre- 
serving it for a long period^ is the plan recommended to bring it>to 
a highly concentrated state; this is done by repeatedly exposing it 
to a sufficient degree of cold to congeal the aqueous and mueila- 
giuous parts; after a crust of ice is formed, the juice is poured into 
another vessel, and by repeating the process several times, the 
remainihg juice becomes highly concentrated, and will keep for many 
years wthout undergoing any change; it is proper to observe, how- 
ever, that the lemon being the produce of the warmer climates, 
there miiy be a difficulty in submitting it to this process previously 
to exportation. In the West Indies, where a considerable quantity 
of this acid is prepared for the use of the navy, under the name of 
lime juice, being obtained from the lime (Citrus Lima,) it is customary 
to boil the juice, and to allow the feculent matter to subside as it 
cools; it is then strained off into casks, and a small quantity of 
sulphuric acid added ; in this way it is imported, and keeps good 
ifor a considerable time.f 
* Pure citric acid, commonly called salt of lemon, is best (obtained 
%y saturating boiling lemon juice with powdered chalk, on which the 
valine compound falls to the bottom and leaves the mucilage sus- 
pended in the fluidj which must be decanted off and the precipitate 
washed till quite clean; then add a quantity of sulphuric acid, equal 
to the chalk in weight, and diluted with ten parts of water, and boil 
it for a few minutes, on which the sulphuric acid combines with the 
chalk, and leaves the citric acid dissolved in the fluid. If this fluid 
be evaporated to the consistence of a syrup, the pure citric acid 
* Forster's Voyage, p. 638. 
t Lemon jaice may also be evaporated by the tieat of the sun, till it forms a solid 
salt ;, in which state it was brought from Jamaica, and found extremely grateful to the 
taste, and 3i dissolved in a quantity of water equal to the juice of a lemon, was ren- 
dered of the same degree of acidity, — See Percioal's Phil. Med. and Exp. Essays, p, 219. 
