MUTUAL ACTION OE LIME AND ALKALI.
43
mediately rendered mild, inactive, and incapable of being diffolved by
pure water.
Here is, therefore, a sudden restitution of the lime to its original
ſtate of a mild, inactive, insoluble earth; for when we collect and
dry the mild earth thus obtained, we find it has every property of the
calcareous earth, in its natural or ordinary ſtate, and may again become
lime by calcination.
But, further, when this change is produced in the lime, the alkali
fuffers one which is as remarkable. This is perceived when we ſepa
rate the alkaline liquor again from the lime, and examine this liquor,
or by evaporation obtain the alkali again in a dry ſtate.
We find it incomparably more fusible than before. It is melted
long before the heat of it is raised to the degree of ignition.
Moreover, it becomes more susceptible of vaporisation. A very
sensible quantity is carried off by hasty boiling the solution of it in
water; and if long continued in a red heat, with spongy matters to
prevent its melting, it evaporates very faſt, and is lost.
We find also that its acrimony, or activity to dissolve different sub
stances, is very greatly increased. In the treatment juſt now mention
ed, —the melting of it by heat,—it often happens, that by raising it to
a red heat, it dissolves the earthen vessel in which it is melted.
Alkali, rendered more active in this manner by lime, is much em
ployed in some of the arts, and, being also used for some purposes in
medicine, is ordered to be prepared in both our pharmacopœias.
Three parts of alkaline salt, and four parts of perfect quicklime,
are to be suddenly mixed in twice their weight of water. This will
produce great heat and ebullition. The vessel must be covered, and
the mixture agitated repeatedly. It muſt then be poured into a fil
trating funnel, which is set into a phial, or other vessel, proper for
holding the lixivium. After it has ceased running through the filtre,
water muſt be poured on a top, and allowed alſo to run through the
filtre, till the whole lixivium is about thrice the weight of the ſalt and
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