CETRAR′IC ACID. H2C18H14O8. Syn. Cetrar′in. The bitter principle of Iceland moss (Cetraria Islandica). It exists, in the free state, in the cortical portion of the thallus.
Prep. 1. Iceland moss (bruised), 1 part; rectified spirit, 6 parts; boil in a covered vessel for half an hour; express the liquor whilst hot, filter, and distil off the spirit; redissolve the residuum in boiling alcohol, decant the clear, and let the solution cool slowly; lastly, collect the crystals and preserve them out of contact with air.
2. (Herberger.) Iceland moss (in coarse powder), 1 lb.; alcohol (·883), 4 lbs.; boil as before, cool until vapours cease to rise, express the tincture, add hydrochloric acid, 3 dr., (dissolved in) water, 2 oz.; let it rest for a night in a closed matrass; then decant, throw the deposit on a filter, press it in bibulous paper, and whilst still moist wash it with both alcohol and ether; lastly, purify it by digestion in boiling alcohol, as before.
Prop., &c. Pure cetraric acid occurs under the form of minute, shining, acicular crystals; it is intensely bitter, non-volatile, scarcely soluble in water, ether, and cold alcohol; soluble in alkaline solutions forming soluble salts, which give a red colour with the persalts of iron, and a yellow one with acetate of lead. The compounds are called cetrarates.—Dose, 2 to 4 gr. every three hours, as a febrifuge; 1 to 3 gr. thrice daily, as a tonic.
CHA′BERT’S OIL. Syn. Chabert’s empyreumat′ic oil; O′leum empyreumat′icum Chaberti, O. contra tæniam Chaberti, L. Prep. (Ph. Bor. 1847.) From empyreumatic oil of hartshorn, 1 part; oil of turpentine, 3 parts; mix and distil over three fourths only in a glass retort, and keep it in well-stopped bottles. In tapeworm.—Dose, 2 teaspoonfuls in water, night and morning, until 4 to 6 or even 7 oz. have been taken; a cathartic being also administered from time to time.
CHAFING. See Excoriations.
CHAIRS. The black leather work of chairs, settees, &c., may be restored by first well washing off the dirt with a little warm soap and water, and afterwards with clean water. The brown and faded portions may now be
retained by means of a little black ink, or preferably, black reviver, and when this has got thoroughly dry, they may be touched over with white of egg, stained and mixed with a little sugar-candy. When the surface is nearly dry, it should be polished off with a clean brush.
CHALK. Syn. Soft carbonate of lime, or Carbonate of calcium, Earthy c. of l.; Cre′ta, L. Chalk is largely used in the arts and manufactures, and in medicine. The natural varieties are remarkable for the fossils which they contain. The COLOURED CHALKS which are used as pigments and for crayons generally contain both clay and magnesia, as well as oxide of iron, and are minerals quite distinct from WHITE CHALK, or CHALK properly so called. The latter is an AMORPHOUS CARBONATE OF LIME. Exposed for some time to a red heat, it is converted into QUICK-LIME; ground in mills and elutriated, it forms WHITING; the same process performed more carefully and on a smaller scale produces the PREPARED CHALK used in medicine. When prepared artificially (by precipitation), it is the PRECIPITATED CHALK of modern pharmacy. (See below.)
Chalk, Black. A variety of drawing slate.