A sweet principle (B.P.). It is a trihydric alcohol, C3H5(HO)3; 92, obtained by reaction of fats and fixed oils with aqueous fluids, and containing a small percentage of water (not less than 95 per cent, of absolute glycerin, U.S.P.)

Characters. - A clear, colourless fluid, oily to the touch, without odour, of a sweet taste.

Solubility. - Freely soluble in water and in alcohol.

Reactions. - When decomposed by heat it evolves intensely irritating vapours due in part to acrolein. Specific gravity 1.25.

Dose. - One half to 2 fl. dr.

Preparations (vide p. 513).

B.P.

Extractum Cinchona Liquidum.

Lamellae, in all.

Glycerinum Acidi Carbolici.

Linimentum Iodi (p. 516).

„ n Gallici.

„ Potassii Iodidi cum Sapone.

„ „ Tannici.

Mel Boracis.

„ Aluminis.

Pilula Aloes et Myrrhae (p. 522).

„ Ainyli.

„ Rhei Composita.

„ Boracis.

,, Saponis Composita.

„ Plumbi Subacetatis.

Tinctura Kino.

„ Tragracanthae.

Unguentum Iodi.

U.S.P

Glyceritum Amyli. Glyceritum Vitelli.

Mucilago Tragacanthffi.

Action and Uses. - Olive oil is used externally in the form of liniments as a lubricating substance, and in seborrhoea it may be applied 4 or 5 times daily till the crusts are removed. It is useful alone in acute attacks of psoriasis and in acute eczema capitis. Internally it acts as a demulcent in cases of irritant poisoning, except by phosphorus. In large doses it is slightly laxative, as in oily salads.

Soft soap is more alkaline than the hard, and from the free potash it contains, it may produce a caustic effect on the skin if too long applied. Rubbed in for 5 or 10 minutes once or twice daily, it is very useful in chronic and subacute eczema, a soothing ointment being applied after its use. A tincture of soft soap (2 in 1 of rectified spirit) is a convenient form of applying it to the hairy scalp: after rubbing in, it must be washed off and an oily preparation used. This treatment does good in seborrhoea, in scaly forms of eczema capitis, and in lupus fur-furacea. Soft soap is also useful in sycosis and ichthyosis and in some cases of lupus erythematosus.

Hard soap is used chiefly as a detergent, and for its mechanical effect, in pills and as an adjunct in suppositories. A small piece of soap cut into a conical form and used as a suppository is very useful in constipation occurring in infants. Soap and water forms a useful enema for constipation in adults.

Glycerin is used as an ingredient in ointments and lotions in various skin-diseases. With two per cent. carbolic acid added, if rubbed on in the bath, it relieves the itching in chronic eczema. Five per cent. glycerin with an equal part of Friar's balsam in rose-water is useful in acne (vide p. 965); glycerin soaps are used in seborrhoea and acne.

Glycerin acts as a laxative, and when used along with castor oil increases its power. It is largely destroyed in the system, has an influence on nutrition, and has been proposed as a substitute for cod-liver oil, but without much benefit. Very large doses cause a red coloration in the urine, due to the colouring matter of the blood, without any free corpuscles.

It is used as a laxative in haemorrhoids; as a solvent of other drugs, as borax, tannic acid; as an emollient to soften the hands, and applied to sore nipples, fissure of the tongue, in advanced phthisis, croup, laryngitis, etc. It has been painted on in eczema, psoriasis, pruritus; also as a preventive of bedsores. It must be diluted with water, or it will irritate the part. It has been proposed as a substitute for sugar in diabetes.