of water and caloric required for solution by each salt, what quantity
of caloric is absorbed by each at the moment of liquifaction, and how
much is disengaged at the moment of cristallization. Hence the reason
why salts are more rapidly soluble in hot than in cold water is
perfectly evident. In all solutions of salts caloric is employed; when
that is furnished intermediately from the surrounding bodies, it can
only arrive slowly to the salt; whereas this is greatly accelerated when
the requisite caloric exists ready combined with the water of solution.
In general, the specific gravity of water is augmented by holding salts
in solution; but there are some exceptions to the rule. Some time hence,
the quantities of radical, of oxygen, and of base, which constitute each
neutral salt, the quantity of water and caloric necessary for solution,
the increased specific gravity communicated to water, and the figure of
the elementary particles of the cristals, will all be accurately known.
From these all the circumstances and phenomena of cristallization will
be explained, and by these means this part of chemistry will be
compleated. Mr Seguin has formed the plan of a thorough investigation of
this kind, which he is extremely capable of executing.
The solution of salts in water requires no particular apparatus; small
glass phials of different sizes, Pl. II. Fig. 16. and 17. pans of
earthern ware, A, Fig. 1. and 2. long-necked matrasses, Fig. 14. and
pans or basons of copper or of silver, Fig. 13. and 15. answer very well
for these operations.
SECT. II.
_Of Lixiviation._
This is an operation used in chemistry and manufactures for separating
substances which are soluble in water from such as are insoluble. The
large vat or tub, Pl. II. Fig. 12. having a hole D near its bottom,
containing a wooden spiget and fosset or metallic stop-cock DE, is
generally used for this purpose. A thin stratum of straw is placed at
the bottom of the tub; over this, the substance to be lixiviated is laid
and covered by a cloth, then hot or cold water, according to the degree
of solubility of the saline matter, is poured on. When the water is
supposed to have dissolved all the saline parts, it is let off by the
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