£28

Materia Medio*.

PART ft.

round cakes, about two or three inches thick, concave on oneside, convex on the other, and generally perforated.

Qualities. — Pure camphor has a strong, peculiar, fragrant,penetrating odour j and a bitter, pungent, aromatic taste. Itis white, transparent, unctuous to the touch, and friable, break-ing with a shining foliated or tabular fracture, which displays acrystalline texture: and although brittle, yet it is also in "somedegree ductile, and therefore not easily pulverised. It swimson water, its specific gravity being O m 9887 z : and is so volatile,that if it be not kept in well stopt vessels, it loses a very consi-derable proportion of its bulk and weight by evaporation. Itmelts at a temperature of 260°, and sublimes in close vessels,crystallizing unchanged in hexagonal plates. It is readily ig-nited, and burns with a brilliant flame, giving out much smoke.When triturated with water, very little is dissolved 1 , althoughit communicates to the water its odour and pungency; but theaddition of carbonic acid gas augments very much the solventpower of water over camphor. Alcohol, ether, the fixed andvolatile oils, the sulphuric and nitric acids a little diluted, andthe muriatic, the strong acetic, and the fluoric acids, dissolvecamphor, which is again separated unaltered from these solu-tions by the addition of water. Concentrated sulphuric aciddecomposes it, forming artificial tannin; and by repeatedlydistilling it with nitric acid, it is converted into camphoricacid. Alkalies exert scarcely any action on camphor : but itunites with, and converts into a soft tenacious mass, the hard-est resinous substances. Camphor, when mixed with clay, anddistilled in close vessels, is decomposed, and resolved into a vo-latile oil and charcoal: hence, as a chemical compound, it ap-pears to differ from the essential oils, only in containing a largerproportion of carbon.

Medical pnrperties anil uses. — Camphor is stimulant, narco-tic, and diaphoretic, but its stimulant powers are very transi-tory, and followed by sedative effects. The Arabians ap-pear to have first used camphor as a medicine', and by themit was regarded as refrigerant; an opinion which, even <n morerecent times, has been the subject of much controversy. Inmoderate doses it operates as a cordial, increasing the heat ofthe body, exhilarating, softening, and rendering fuller the pulse,and promoting diaphoresis: in larger doses it allays irritation,and spasm, abates pain, and induces sleep. But in immoderate

i Brisson.

* Ca'let asserts that one French pint of water dissolves about sixteen grains of cam-phor, which are again precipitated by pure potass. Arm. de Chimie. lxii. 132.t They called it Canfut as well as Cafoai. Clusivs Eiot. 34*, quoted by Alston.