Conspectus of the pharmacopoeias of the London, Edinburgh, and Dublin Colleges of Physicians ... / [Anthony Todd Thomson].

  • Thomson, Anthony Todd, 1778-1849.
Date:
1830
Catalogue details

Licence: Public Domain Mark

Credit: Conspectus of the pharmacopoeias of the London, Edinburgh, and Dublin Colleges of Physicians ... / [Anthony Todd Thomson]. Source: Wellcome Collection.

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    as used by the Edinburgh College, is preferable, «ns it implies their character, and as some of the volatile oils also arc obtained by ex- pression. Tliose whicJi arc expressed without licat are to be preferred, as by heat they are apt to acquire acrimony and an cmpyrcumatic odour. The greater number of them, when pure, are liquid in a moderate temperature, unctuous, perfectly transparent, colourless, or of a pale yellow or greenish tinge; inodorous; lighter than water, and not miscible willi it : they unite with alkalies and form soap; and with oxyd of lead and form plasters. Almond and olive oil should be insipid ; linseed and castor oils have some taste, but they should not feel hot nor acrid in the throat. Palm oil is a soft solid. The rancidity of oils depends on the absorption of oxygen, on which account they should be kept in bulk as much as possible, and in narrow-necke<l bottles; so that a very small surface only will be exposed to the air. DISTILLED OILS. For similar reasons as those stated above, regarding expressed oils, we prefer the title of the Edinburgh Pliarmacopccia, volatile oiht for these preparations. They are compounds of oxygen, hydrogen, and carbon; and are produced by nature in various parts of the vegetable system ; either in the flowers, the fruit, the leaves, or the hark, and sometimes in all of these parts. The majority of them arc obtained by distillation, but some of them by expression. They pos- sess the unctiiosity, inflajnmability, and viscidity of the fixed oils; but they arc in general coloured, odoriferous, pungent, and acrid. The majority are lighter than water, hut some of tlicm are heavier, and some congeal at a moderate temperature. Tliey arc dissolved in small quantity, in distilled u'utei’, by simple ^ngitatiou. Almost all of them are soluble in alcohol, and miscible with fixed oils, and with each other; hence they are often adulterated with alcohol, or with oil of olives or of almonds, or with oil of turpentine, which is the cheapest of the essential oils. The first is discovered by an increase of temperature and a milky appearance, when the oil is mixed with water; the second, ])y a greasy sUiin being left on paper on which the oil is dropped and exposed to a considerable heat, and by not being soluble in alcohol; and the third, by its odour, when the suspected oil is dropped on paper and lieated, or sometimes even when rubbed be- tween the fingers. The odour and taste are the usual tests of their goodness; and to preserve them, they should be kept in a cool place, in small bottles, quite full, and well corked. DISTILLED WATERS. In tlic distillation of essential oils, the water, which comes over during the process, contains dissolved in it a portion of the oil, and forms this class of preparations. I'hey should, therefore, have the