. BOTANIC PHYSICIAN. 
_ solid the solvend or body dissolved. The attraction, however, whence 
the solution proceeds, is reciprocal, and is not more exerted by the 
one than by the other. — z a 
__ The previous mechanical division of solids, promotes their solu- 
d. Agitation causes the solution to proceed more rapidly, 
‘here are, in general, certain limits to the solution of solids in 
fi _ A certain quantity of sea-salt, for example; may be dissolved 
- ina given quantity of water; but if more be added, it remains un- 
dissolved, and can only be diffused through the solution. When the 
fluid has taken up as much of the solid as it ean dissolve, it is said to 
be saturated withit. The same fluid requires for its saturation very 
different quantities of solids; of some it can dissolve only a very 
all portion, of others more than its own weight. The saturation 
fluid with one substance, does not prevent it from dissolving a 
on of a second, or even of a third or fourth, though it lessens 
rent power with regard to each. There are some cases in 
“ the solvent power is apparently unlimited, or in which no pre- 
cise point of saturation can be pointed out, such as the solution of 
sugar, gums, &c. in water, ; 
The temperature or degree of heat has a very important influence 
on solution, and in varying the point of saturation. In general every 
___ Solution proceeds with more facility or rapidity at a high than ata 
s low temperature, and the fluid is even capable at the high tempera- 
: ‘ture of dissolving a larger portion of the solid, though with respect to — 
different solids, this increase of solvent power, by a given’ tempera- 
ture, is very different. : i 
__ Solution, besides being one of the most important operations im 
ucal analysis, is one of the most useful in pharmacy, the active 
principles of many substances being extracted, by means of their — 
proper solvents. Saline substances are dissolved in water, as are 
also gum, sugar, and other vegetable and animal products. Resins, — 
camphor, essential oils, &c. are dissolved in ether, alcohol, or wine; 
and metals are rendered soluble and active by the different acids. 
The operation receives different appellations, according to the na- 
ture of the solvent, of the substances dissolved, and of the manner in 
which it is performed. When we have a mixture of saline or earthy 
“Substances, of which part is soluble in water, or in any other fluid, — 
_ while another part is insoluble, the one may be separated from the — 
by the due application of its Proper solvent. ‘Che process thus 
ed is termed Lixivratrton, and the solution obtained, a LEY. _ 
rhen a fluid is poured on any vegetable or animal substance, 80 a8 
to dissolve only part of its principles, the operation is termed EX- 
TRACTION; and the part dissolved is said to be extracteds. If it is 
performed without the assistance of heat, it is termed MACERATION 5 
if with a moderate heat, pigestion ; if the fluid be poured boiling 
hot on the substance, and they are kept in a covered vessel till cold, 
it forms inrustox. Lastly, pecoctton is the term given to the op 
ration where the fluid is boé/ed upon the substance to be dissolved. 
To obtain the solid matter which has been dissolved in any 
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