. An introduction to practical pharmacy [microform] : designed as a textbook for the student and as a guide to the physician and pharmaceutist : with many formulas and prescriptions . 0. tracts is rendered tedious by the lowtemperature employed, the rapidity ofevaporation being in proportion to thetemperature, thus: at 180°, the rate ofevaporation is only one-half what it isat 212°; and at 150°, it is only one-half Berlin evaporating dish. what it is at 180°. The long eXpOSUM of a vegetable solution to a moderateheat, besides being so tedious, is liable to objections of exposingthe proximate c
. An introduction to practical pharmacy [microform] : designed as a textbook for the student and as a guide to the physician and pharmaceutist : with many formulas and prescriptions . 0. tracts is rendered tedious by the lowtemperature employed, the rapidity ofevaporation being in proportion to thetemperature, thus: at 180°, the rate ofevaporation is only one-half what it isat 212°; and at 150°, it is only one-half Berlin evaporating dish. what it is at 180°. The long eXpOSUM of a vegetable solution to a moderateheat, besides being so tedious, is liable to objections of exposingthe proximate constituents present for a long period to the oxidiz-ing influence of the air, sometimes even producing the acetous fer-mentation. The liquid to be evaporated should be divided into comparativelysmall portions, and each reduced separately till it is highly concen-trated ; then the whole may be mixed. By this means, no one por-tion is kept a very long time under the unfavorable circumstancesof an elevated temperature and exposure to the air. A draught greatly facilitates evaporation by carrying off the air asfast as it becomes charged with moisture, and constantly furnishing. IMPROVED APPARATUS. 153 Fig. 151. a dry atmosphere to become saturated in turn with the escapingvapor. Constant stirring, by continually exposing a large surfaceo? the heated liquid to the air, also increases the rapidity of evapo-ration. The different modes of applying heat for the purposes of evapo-ration, are: 1st. Directly by exposing the containing vessel to thesource of heat. 2d. By a sand bath. 3d. By a water bath. a steam bath. Whenever a vegetable solution is evaporated by a direct appli-cation of heat, it should be at such an elevation from the furnaceor lamp, as not to be touched by theflame, so that the heat should be com-municated by radiation. When theheat is under perfect control, as in agas furnace, this plan is not objection-able, and may be substituted for theuse of a water bath
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectpharmacy, bookyear185
