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Preparations and Compositions. Part III.
which lose their virtue by drying, lose it equally on beingsubmitted to this treatment with the purest alcohol.
In this way the alcoholic extract of some aromatic sub-stances, as cinnamon, lavender, rosemary, retain a consider-able degree of their fine flavour.
In the second case, the alcohol need not be so very strong,because it is capable of dissolving resinous substances, al-though diluted with a considerable proportion of water.
In the first case, the alcohol may be still much weaker;or rather, the addition of a small proportion of alcohol to wa-ter will be sufficient to retard or prevent the decomposition ofthe decoction.
The alcohol employed in all these cases should be perfectlyfree from any unpleasant flavour, lest it be communicated tothe extract.
The inspissation should be performed from the beginning,in the gentle heat of a water-bath. We need not suffer thealcohol to evaporate in the air : the greatest part of it may berecovered by collecting the vapour in common distilling ves-sels. If the distilled spirit be found to have brought over anyflavour from the subject, it may be advantageously reservedfor the same purposes again.
When diluted alcohol is employed, the distillation shouldonly be continued as long as alcohol comes over; and theevaporation should be finished in wide open vessels.
In this chapter we have also included the processes in-tended for purifying inspissated juices and resinous sub-stances.
Pure resins are prepared, by adding, to spiritous tincturesof resinous vegetables, a large quantity of water. The resin,incapable of remaining dissolved in the watery liquor, sepa-rates and falls to the bottom ; leaving in the menstruum suchother principles of the plant as the spirit might have extractedat first along with it. But this is only practised for the pur-pose of analysis.
EXTRACTS MADE WITH WATER.
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EXTBACTUM GENTIANS LUTE^I. Ed.
Extract of Gentian.Take of
Gentian root, any quantity.Having cut and bruised it, pour upon it eight times its weight