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Show Bic rr a J “a lasae SS ae mm} 118 COMMON PERUVIAN BARK TREE. COMMON PERUVIAN BARK TREE. turnsole, others do not affect it; some impart a deep colour to water, others verylittle; some affect certain metallic solutions, which others do not; and the decoctions of some kinds remain transparent after becoming cold, others grow turbid as they cool, and deposit a copious precipitate. The following mode of analysis, however, will give an idea of the composition of the second class :—The cold infusion has a red colour, more or less of tan, and of some varieties of cinchona. This salt M. Vauquelin discovered to consist of lime, and a new acid which crystallizes in plates, has a very acid taste, forms soluble and crys stallizable combinations with the alkalies and earths, and does not precipitate the nitrates of silver, mercury, or lead. M. Vauquelin has given it the name of Kinic acid; but as this would lead us to suppose that it was obtained from Kino, it appears to me that it ought to be named the cinchonic acid, from the systematic name of the tree from whose bark it has been first obtained. M. Vanquelin. has also analysed the barks of the cinchona pubescens and officinalis, which he refers to the first class. In almost every respect the analysis agrees with that now detailed, except in the chemical properties of the deposit from the concentrated infusion, which in the present instance produces a copious precipitate in the infusion of nut-galls, as well in tartar emetic and nitrate of mercury. ‘These deposits, he observes, differ from resins in being soluble in water, in acids and in alkalies, in acting as adye, in decomposing metallic solutions, and in their watery solution becoming mouldy. He is inclined to consider them as a peculiar vegetable principle, not yet suffi. ciently examined. Having thus detailed the latest experiments on this important brown oryellow; bitter taste, with more or less astringency ; becoming in a few days covered with ‘a green mould. On evaporating the infusion, if it be permitted to cool repeatedly during the process, it becomes turbid, and deposits a precipitate for several times. If these precipitates be separated, and the Supernatant fluid, after it ceases to become turbid oncooling, be evaporated to the consistence of a soft extract, and treated with alcohol, there remains only a viscid substance of a brown colour, almost without bitter taste, insoluble in alcohol, perfectly soluble in water, not rendering it turbid on cooling, and which, by spontaneous evaporation, is analysed into a saline mass, consisting of reddish brown crystals, hexahedral, rhomboidal, or square, and a mucilaginous matter which remains dissolved in the mother-water. The precipitate which is deposited on the cooling of the concentrated infusion, when dried, has a red brown colour and an intensely bitter taste. It is readily soluble in alcohol, especially whenheated. The tincture is decomposed by water, and yields crystals on spontaneous evaporation. It is sparingly and only partially soluble in cold water, more copiously and completely in boiling water, which, however, again becomes turbid on cooling. Its solution reddens tincture of turnsole, grows mouldy in a few days, does not precipitate tartar emetic, or solution of gelatine; is not visibly acted upon by acids, but with alkalies is coagulated into a thick whitish matter, becoming brownand somewhat hard by exposureto the air, softening with heat, and acquiring the ductility and silky gloss of turpentine. Thesaline mass whichcrystallizes from the mother-water, on being purified by repeated solutions and crystallizations, is ob- tained in the form of white square or rhomboidal plates, often grouped, with almost no taste, soluble in about five waters at 50°, insoluble in alcohol, destructible byfire, not decomposed by ammonia, acetate of lead, or nitrate of silver, but by the fixedalkalies, and theoxalic and sulphuric acids, and by infusion 119 subject, it may not be superfluous to notice the observations of preceding chemists, with a view of rendering the history of the analysis of cinchona more perfect. Neumann got from 7680 parts of common cinchona 640 alcoholic, and afterwards 300 watery extract; and inversely, 330 watery and 600 alcoholic; from whichit might be inferred, that there were about 600 parts soluble in alcohol only, 300 in water only, and 30 or40 in both; but the proportion of the last is certainly too small. Fourcroy extracted from 576 parts of red bark, 38 by water, and afterwards 24 by alcohol. Marabelli got from a poundof yellow bark, 464 grains of gum, 470 of extractive mucous mate ter, 292 of extractive resinous matter, and 125 of resin, besides saline matters, &c. Lewis observed that the decoction became turbid on cooling, and that the precipitate was soluble in alco- hol, He also pointed out the deep green colour which decocons of cinchona acquire from the addition of chalybeates. Dr. Irving afterwards found that recent decoctions gave a black co‘Our, while those which had been kept some time gave a green, |