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Show 134 RED PERUVIAN BARK RED PERUVIAN BARK TREE. TREE. Form a powder, to be taken three times or four times a day. This is excellent in obstinate diarrhoea, first evacuating with rhubarb and colombo, equal parts, three grains every four hours. R.. 4. Take of bark, in powder, - - scruples 2, cascarilla, in powder, - grains 10: Form a powder, to be taken every six hours in a glass of red wine. In low nervous fevers. R.. 5. Take of decoction of bark, lime water, equal parts, a pint: A full wine-glass is to be taken four timesaday. This is found frequently to remove obstinate scabies, commonly called violent scorbutic eruption. Bark is usefully joined with calcined magnesia. Two drachms of Peruvian bark in powder, and half a drachm of calcined magnesia, were rubbed together in a mortar, with four ounces of distilled water, for the space of ten orfificen minutes; the water being gradually added, so as to reduce the materials in the first instance to the state of a paste. The infusion, when passed through filtering paper, is found to be possessed of the following remarkable properties : ist. An exceedingly deep red colour, superior to the infusion of common barkin lime water. Qd. It is more bitter and astringent to the taste even than an infusion of red bark. 3d. It produces a very deep black colour, with a copious precipitation, upon the addition of a solution of sal martis ; while a similar addition to a common infusion of bark occasions a moderate discoloration and small precipitation only. tth. It remains beautifully transparent three or four days, and is so strongly antiseptic, that at the end of a week, in summer, it had scarcely made any advances towards fermentation ; while an infusion of bark with simple waterwill ferment in twodays. 5th. It exceeds in specific gravity the infusion of bark in lime water, in the same, or rather in a greater proportion, than that In order to determine moreparticularly the nature of the infusion prepared by diately discharged the red colour, and caused a whitish precipitation: hence it is obvious that magnesia not only increases the activity of water upon bark, but is in fact dissolveditself in the water in a very small proportion. If calcined magnesia be added to an infusion of bark, prepared in the common way with simple water, it occasions no change in its colour or properties; from which we may conclude that when bark and magnesia are rubbed together with water, in the manner before mentioned, the magnesia either enables the water to extract something from the bark, which it could not have done alone, or, what is more probable, by uniting chemically, they form a compound more active and soluble in water than pure bark, With a view of ascertaining how far the colouring matter of an infusion of bark with magnesia corresponds with the astrin- gencyof it, the following experiment was made :—The clear and colourless liquor was carefully poured off from the precipitate, which the acid of sugar had occasioned when added to the infusion of bark and magnesia, and being mixed with a proper quan- tity of the chalybeate solution changed to a green colour only; from which circumstanceit is probable that there is a close connection between the colouring matter and astringency, for the deeper the red colour of the infusion, the more complete always is the black which the chalybeate produces. Magnesia differs remarkablyfromlime in its action upon bark ; for, whether in a small or large quantity, it promotes thesolution, though more completely as the proportionis greater. By the addition of half a drachm, or a drachmat the utmost, however, to two drachms of bark and four ounces of water, thefull effects are obtained, and an additional quantity of the magnesia would only be wasted. I have mentioned that the magnesia, with which the experiments hitherto related, was calcined. I mayadd, that it was prepared by my friend Mr. Babington with the greatest care, so as to have lost more than half its weight by calcination. exceeds the simple infusion. the last experiment, several additions were 138 It was next an object to try the action of common magnesia upon bark, in order to determine howfar the presenceor absence of fixed air Being mixed in equal quantities could assist in the explanation of the effects which have been with water impregnated with fixed air, no othereffect was pro- enumerated. One drachm of common magnesia (which is about equal to half a drachmof the caleined) was rubbed in a mortar fifteen made to different portions of it. duced than that of simple dilution. A small quantity of the acid of sugar, however, being added to some ofthe infusion, imme- |