Elements of the Theory and Practice of Chymistry, 5th ed.Macquer, Pierre Joseph
History
Elements of the Theory and Practice of Chymistry, 5th ed.
Macquer, Pierre Joseph
Chemistry -- Early works to 1800
I myself have made several experiments in order to get some insight
into the saline nature of Lime, and shall here produce the result
with all possible conciseness. I took several stones of different
kinds, some of which produced by calcination a very strong Lime, and
others but a very weak one. These I impregnated with different saline
substances, acids, alkalis, and neutrals, and then exposed them all
to the same degree of fire, which was a pretty strong one, and long
enough continued to have made very good Lime of stones the most
difficult to calcine. The consequence was, that, in the first place,
those stones which naturally made but a weak Lime were not, by this
process, converted into a stronger Lime; and, moreover, that none of
these stones, even such as would naturally have produced the most
active Lime, had acquired the properties of Lime. These experiments I
varied many ways, employing different proportions of saline matters,
and almost every possible degree of fire, and constantly observed,
after calcination, that all those stones were so much the farther from
the nature of Lime, as they had been combined with larger doses of
salts. Among those which were impregnated with the greatest proportion
of salts, and had suffered the greatest violence of fire, I observed
some that had begun to flow, and were in a manner vitrified. Now, as
the same subject cannot be, at one and the same time, in the state
of glass and of Lime too; as a body cannot approach to one of these
states but in proportion as it recedes from the other; and as salts in
general dispose those bodies to fusion and vitrification which are in
themselves the most averse to either, I concluded from my experiments,
that the saline substances I used, had, by acting as fluxes upon the
stones, prevented their calcination; that consequently we may suspect
there is no saline matter in the composition of Lime, as Lime; and that
Lime does not owe its saline and alkaline properties to any salt; or at
least that, if it does owe those properties to a salt, such salt must
be naturally and originally combined with the matter of the stone in
so just a proportion, that it is impossible to increase the quantity
thereof without prejudicing the Lime, and depriving it in some measure
of its virtue. This theory agrees perfectly with the illustrious
Stahl's opinion; for he thinks, as we observed in discoursing of salts
in general, that every saline substance is but an earth combined in
a certain manner with water. This notion he applies to Lime, and
says, that fire only subtilizes and attenuates the earthy matter, and
thereby renders it capable of uniting with water in such a manner, that
the result of their combination shall be a substance having saline
properties; and that Lime accordingly never acquires these properties
till it be combined with water.
Public-domain text, read in full here on John Shaqi.
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