Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 2, 1802).djvu/124

104] intermission, it may be considered as an indication of the return of appetite, and they ought to be satisfied either by the breast, or other means; but, if they vociferate quickly and abruptly, it may be reasonably supposed to proceed from a sense of pain. Circumstances of this nature claim the most diligent attention of mothers and nurses. We therefore earnestly enjoin them, particularly the former, to study the exact distinction of the different sounds expressed by their infants; as the result of such inquiries would greatly enable the medical assistant to ascertain, with more precision, the true cause of infantine diseases.  CRYSTAL, a species of stone, of various colours, of which that most generally known is the pebble-crystal, or sprig or rock-crystal, as it is usually called. It is common in this country, and is frequently cut into chandeliers, vases, lustres, and other ornamental articles. Even this hard and beautiful mineral has often been used in medicine, as an astringent and lithontriptic: it was formerly given in diarrhœas, and in cases of stone in the kidnies. The dose usually prescribed is from 20 to 30 grains, finely pulverized by repeatedly calcining and plunging it in cold water. It has likewise been recommended as a dentrifice, but like other hard bodies, it is apt to corrode the teeth, and consequently renders them more liable to decay.  CRYSTALLIZATION, a kind of congelation of essential, fixed, and volatile salts, which, after evaporating the greatest part of their humidity, are left to dry, concrete, and shoot into crystals.

Opaque stones, pyrites, and minerals, when regularly formed, are said to be crystallized, as well as transparent salts and stones. Ice is a true crystallization, consisting of long masses flattened on one side, and joined together in such a manner, that the smaller are inserted into the sides of the greater, making uniformly the same angle. Melted metals, and other bodies, such as wax and starch, which become solid when congealed, assume a regular arrangement, if gradually cooled.

In order to perform this process in perfection, the evaporation should be gentle, and not continued longer than till some drops of the liquor, poured on a glass plate, discover filaments of crystal. As soon as this appears, the vessel is to be immediately removed from the fire into a cooler place, and covered with a cloth, to prevent the access of cold air, which would form pellicles. From a variety of experiments, we have observed that crystallization may be remarkably promoted, by throwing into the vessel a few small crystals of the same nature.

Another method of crystallizing salts, is, by adding to a solution of salt a substance which does not act upon the latter, but which has a greater affinity with the water, and will serve to deprive the salt of a portion of that liquid which holds it in a state of solution. Spirit of wine will effect this purpose in many salts; and, if judiciously added, will cause them to separate freely from the menstruum, or fluid, and form large and beautiful crystals.

Salts have this peculiar property, that, however minutely they may be divided, when formed into crystals, they will re-assume their proper