940
ELEMENTS OF MATERIA MEDICA.
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process of sublimation, good benzoin yields 10 to 12 per cenl ' . ve eiicontaminated by empyreumatic oil, and which, when pressed o ^ o)1folds of blotting-paper, and again sublimed, is reduced to the P V^igtrytof 8 or 9 per cent, of the purified acid” (Brande, Manual of C'Afi 77 * .p. 975,4th ed.) The simplest method of procuring it is by putting coa ^powdered benzoin into an earthen pot, over which is placed abrown paper, and applying a moderate heat: the acid sublimes in e>cone, and there condenses. Some employ, as a substitute for thea house, as it is termed, made of pasteboard and laths, and line gloose sheets of blotting-paper, which are renewed every time of use- ^oil produced in sublimation is, for the most part, formed duringprocess. tfoiU
Scheele’s process, adopted by the Dublin College, is, I believe, B , efollowed. By boiling benzoin and lime with water, a soluble ^”^<1of lime is formed. Muriatic acid is then added to the concen ^solution, by which benzoic acid is precipitated, while chloride of ca . j j s(in solution) and water are formed. The precipitated benzoic a . ^then sublimed. The acid obtained by this process is said to be u ^and purer (being free of empyreumatic oil) than that procured b) - ulimation only. Carbonate of soda is sometimes substituted for mthe above process, by which a soluble benzoate of soda is obtaine • jGood benzoic aeid has the following properties :—It is colourless jis sublimed entirely by heat ( Edinb . Pharm.) When cautiously hit totally evaporates with a peculiar odour. It is sparingly s°m j u .water, but plentifully in rectified spirit. It is entirely dissolved bytion of potash or lime-water, and is precipitated by hydrochloric ,{Pharm. Lond.) The other properties of the acid have been adescribed (see p. 937). .
The local action of benzoic acid on the body is that of an 11 Q fthus when swallowed it causes a sensation of acridity in the back Pthe mouth and throat, and of heat in the stomach. Its vapour,inhaled, is exceedingly irritating, and causes violent coughing-remote effects are those of a stimulant, whose influence is p nnC *directed to the mucous surfaces, especially the bronchial membrane- ^Alone it is rarely employed in medicine. Formerly it " aS o j.mixed with gum or sugar, in doses of from grs. v. to 3j. in chronny ^monary affections. Its principal use now is as a constituent otinctura camphorce composita (see p. 797).
Order 44. Pyrola'ce.e, Lindley. —The Winter Green Tkib®'
Essential Character. Calyx free, four-, more frequently five-partite, P e ^ W f,wPetals five, free or cohering, perigynous ? with an imbricated oestivation. - u lar,twice the number of the petals, to which they are not adherent; anthers hidehiscing by two pores. Ovarium three- to five-celled, seated on a bypogy' l0 7 uS |hree -Style one. Stigma roundish or lobed, sometimes slightly indusiate. Capsnwto five-celled, three- to five-valved, loculicidal-dehiscent. Placenta adherent acentre. indefinite, minute, with a pellicle indusiate or winged. ^
nute, at the base of fleshy albumen, with moderately distinct cotyledons.—"natives of the northern hemisphere, perennial or scarcely under -shrubs, SI1 ^, 0 sc,Stems round, naked or leafy. Leaves simple, entire or dentate. Flowers r * c< L%).somewhat umbellated, rarely solitary, white or rose-coloured (D.C. Prodr. vii- • 'Properties.— See Chimaphila umbellata.