Sal, (from to purge).
Called also amarus sal, magnesia vitriolata, Ebshamen-sis, and Epsomensis sal. Purging salt, Epsom salt, and English salt. This salt was first obtained from the mineral water at Epsom: it was afterwards separated from the brine which remains after the crystallization of common salt, and the latter is now in general use. It is composed of the vitriolic acid and magnesia; differing from the natron vitriolatum, which has a mineral alkaline salt for its basis. The first is often sold for the latter; but they are distinguished by adding any alkaline salt to a solution of the former, when the earth will be precipitated.
It is with this salt that the purging mineral waters are frequently impregnated, and to which they often owe their virtue. It hath a bitter taste, is soluble in less than twice its weight of water, shoots into long prismatic crystals, liquifies and bubbles in a moderate heat, emitting a quantity of aqueous vapours; it changes to a white spongy mass, which is more bitter than the original salt.
If this salt is dissolved in water and crystallized afresh, it concretes into a larger kind of crystals, which resemble the purging salt usually called Glauber's. It has a nauseous bitter taste; is a gentle purgative, operating in general with ease and safety, yet with a sufficient efficacy, and quickly finishing its operation. Two or three drachms, dissolved in a pint of water, operate more powerfully and easily than a larger quantity in three or four ounces. Its passing off hastily, and not exciting the action of the intestinal fibres, seem to be its principal imperfections. In small doses often repeated it promotes the secretions in general, and proves an excellent aperient in many chronical disorders. It seldom occasions gripes or sickness, like resinous purges. If the patient keep warm, small doses will excice perspiration; if cool, they pass off by urine. As a purge, from an ounce to an ounce and a half is a full dose, which, when dissolved in a quart of water with a drachm of mace or of cardamom seeds previously infused in it, sits easy on the stomach. See Lewis's Mat . Med. Neumann's Chem. Works.
Catharticus Hispanicus sal. It is produced near Madrid from some springs: it is neutral, and agrees with the natron vitriolatum, or Glauber's salt. Its operation is very gentle.
Catharticus Glaureri sal. See Glauberi sal.