“By allowing the pressed sheet of pepsin to get perfectly air-dry—whereby it becomes coated with a white film and small crystals of chloride of sodium—and by immersing it then in pure water for a short time, the greater part of sodium chloride can be extracted, but it has to be done very rapidly, as the pepsin swells up considerably and loses its tenacity.
By operating in this matter I have obtained a pepsin which dissolves in acidulated water to quite a clear colourless liquid, but as it still contains traces of salt, I prefer to call it purified pepsin.”
3. (B. Ph.) A preparation of the mucous lining of a fresh and healthy stomach of the pig, sheep, or calf. The stomach of one of these animals, recently killed, having been cut open and laid on a board with the inner surface upwards, any adhering portions of food, dirt, and other impurity, are to be removed and the exposed surface slightly washed with cold water; the cleansed mucous membrane is then to be scraped with a blunt knife or other suitable instrument, and the viscid parts thus obtained is to be immediately spread over the surface of glass or glazed earthenware, and quickly dried at a temperature not exceeding 100° F. the dried residue is to be reduced to powder, and preserved in a stoppered bottle.—Dose, 2 to 5 grains.
Pepsin, Saccharated. To work it into saccharated pepsin (‘American Journal of Pharmacy,’ January, 1871) the damp pepsin, as it is taken from the press, is triturated with a weighed quantity of sugar of milk to a fine powder, which, when it has become air-dry, is weighed again, the quantity of milk sugar subtracted, and so the amount of pepsin found. The strength of this dry pepsin is now ascertained by finding how much coagulated albumen it will dissolve at a temperature of 100° F. in five or six hours, and after this sufficient milk sugar is added to result in a preparation of which ten grains will dissolve one hundred and twenty grains of coagulated albumen, and this preparation I have called saccharated pepsin.
Pepsin with Starch. Pepsin mixed with starch is the medicinal Pepsine of M. Boudault; the Poudre nutrimentive of M. Corvisart.
PERCENTAGE. Literally, “by the hundred.” In commerce the term is applied to an allowance duty or commission on a hundred. (Webster.)
PERCHLO′′RATE, Syn. Perchloras, L. A salt of perchloric acid.
The perchlorates are distinguished from the chlorates by their great stability, and by not turning yellow when treated with hydrochloric acid. Like the chlorates, they give off oxygen when heated to redness. They may be prepared by directly neutralising a solution of the acid with a solution of the base. See Potassium (Perchlorate of), and Chlorine.
PERCHLO′′RIC ACID. See Chlorine.
PERCOLA′TION Syn. Method of displacement. A method of extracting the soluble portion of any substance in a divided state, by causing the menstruum to filter or strain through it. The ‘sparging’ of the Scotch brewers is an example of the application of this principle on the large scale. In