248

M i.

ACAGIiE GUMMI.

Gum Arabic.

L. (Acacia vein.) Mimosa. Nilotica. E. I),

§

1 »-.-

Qualities, ft is dry, semitransparent, brittle and insipid; by expo'•ure to the air it undergoes no other change than loss of colour. Specifr.Gravity 1.515. Solubility. It is soluble in water in every proportion,forming a viscid solution, (mucilage.) One part dissolved in six ofwater affords a fluid of the consistence of syrup; and in two parts, ;imedium well calculated for die union of dry powders. Gum is also solu-ble in pure alkalies and lime water, as well as in vegetable acids, espe-cially vinegar, with which it forms a mucilage that may be used as a ce-ment like the watery solution, and with the additional advantage of notbeing susceptible of mouldiness.* It is insoluble in alcohol, as well as inaether and oils. By strong sulphuric acid the gum is decomposed and aconsiderable proportion of carbon deposited.t For a farther historyof its habitudes see Mucilago Acacia. Medicinal Uses It is de-mulcent and nutritious ; although it appears in certain states of the bodyto pass through the bowels without change. When triturated with guni-resias it assists their mechanical division, as in Form: 30. OfficinalPreparations. Mucilago Acacia;. L. E. D. Etnuhio Mimosa: Nilo-tica;. E. Emulsio Arabica. D. Mist. Corn. ust. L. D. (O) Mist.Greta. L. D. (©) Mist. Moschi. L. (O) Confect. Amygdal. L. (O) Pulv.Cret. co. L. (C) Pulv. Tragacanth co. L. (B) Trochisci Carbonat.Calcis E (©) Trocli. Glycyrrh. Glob. E. (O) Glycyrrh. cum Opio.E. (O) Troch. Gummas E (O) Adulterations. Gum Senegal isnot unfrcquently substituted for it, but this may be distinguished by itsclammy and tenacious nature ; whereas genuine gum arubic is dry andbrittle ; the fraud is of no consequence in a medical point of view. Itis also occasionally mixed with the gum of plum and cherry trees ;this fraud, however, is to be easily detected, for such gum has peculiarproperties by which it may be chymically distinguished •, see MucilagoTragacanth.

ACETICA. L.E.I). Preparations of Vinegar.

These preparations consist of vegetable principles dissolved in vine- ,gar. Officinal Preparations. Acetum Aromaticum. E. AcidumAcctosum camphoratum. E. Medicated vinegars were formerly much ex-tolled ; the first London Dispensatory contained no fewer than ten, atpresent the number is reduced to two, viz. Acetum Colchici. L. Acetumticilla: L.E.D. which see.•

ACETIS IIYDRARGYRI. E. Acetas Hydrargyri. D. Atetattof Mercury.

Qualities. Form, small flaky crystals; Colour, silvery white;

* Mouldiness is a peculiar plant, propagated by seeds, infinitely small; Reaumurfound the interior of an addled es"g" mouldy, hence the seeds must have passed throughthe pores of the shell ! Dr. Maccultoch has lately announced the curious fact, thattiie propagation of mouldiness may be prevented by the presence of aromatic sub-stances, seep. 182, Me.

+ This fact has enabled the Chymist to prepare an indelible mk ; not affected byBcids.