CETRAR′IC ACID

H 2 C 18 H 14 O 8 . Syn. Cetrar′in . The bitter principle of Iceland mo ( Cetraria Islandica ). It exists, in the free state, in the cortical portion of the thallus. Prep. 1. Iceland mo (bruised), 1 part; rectified spirit, 6 parts; boil in a covered ve el for half an hour; expre the liquor whilst hot, filter, and distil off the spirit; redi olve 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 mo (in coarse powder), 1 lb.; alcohol (·883), 4 lbs.; boil as before, cool until vapours cease to rise, expre the tincture, add hydrochloric acid, 3 dr., (di olved in) water, 2 oz.; let it rest for a night in a closed matra ; then decant, throw the deposit on a filter, pre 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., . 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.