3917. To Obtain Carbolic Acid

3917.     To Obtain Carbolic Acid. This is obtained from that portion of coal-tar which distills over between 300° and 400° Fahr.; this, when mixed with a hot concentrated solution of hydrate of potassa, is resolved, on the addition of water, into a light oil and a heavier alkaline liquid. By separating the latter, and neutralizing it with muriatic acid, impure carbolic acid will float on the surface in the form of a light oil. If this bo distilled from dried chloride of calcium to separate the water, and the distillate be exposed to a low temperature, carbolic acid congeals in a colorless deliquescent crystalline mass, which may be separated from the liquid by pressure in bibulous paper. At 95° Fahr. the crystals melt and constitute the liquid carbolic acid. The introduction of a crystal of carbolic acid into the acid to be congealed, greatly facilitates its crystallization.

3918. Tests for the Purity of Carbolic Acid

3918.   Tests for the Purity of Carbolic Acid. If it becomes brown under the influence of light and air it is impure.

Pat 1 fluid drachm of the liquid acid in a bottle with 1/2 pint warm water, and shake occasionally for half an hour; the amount of oily residue will indicate the measure of adulteration.

Mix 1 part caustic soda with 10 parts of the acid, and shake them well together. Any undissolved residue is impurity.

3919. To Remove the Odor from Carbolic Acid

3919.   To Remove the Odor from Carbolic Acid. It may be interesting to know of a method which will entirely remove this odor, substituting for it a delicate trace of geranium leaves, which may, perhaps, be improved upon by adding a few drops of that oil. The process, as recently published by Professor Church, consists in pouring 1 pound of the best carbolic acid of commerce (the white crystallized) into 2 gallons cold distilled water, taking care not to permit the whole of the acid to enter into solution. "With a good sample, if, after shaking repeatedly at intervals, between 2 and 3 ounces of the acid remain at the bottom of the vessel used, this will be a sufficient residue to hold and contain all the impurities; with bad samples, less water must be used, and more acid. The watery solution is to be syphoned off, and filtered, if necessary, through fine filtering paper, till perfectly clear. It is then placed in a tall cylinder, and pure powdered common salt added, with constant agitation, till it no longer dissolves. On standing for a time, the greater part of the carbolic acid will bo found floating as a yellow oily layer on the top of the saline liquor, and merely requires to be removed to be ready for use. As it contains 5 per cent. or more of water, it does not generally crystallize, but it may be made to do so by distilling it from a little lime. The portion collected has, at ordinary temperatures, and up to 365° Fahr., scarcely any odor save a faint one resembling that of geranium leaves. The addition of about 4 drops per fluid ounce of the French oil of geranium will still further mask the slight odor of the acid, and has an additional advantage of liquefying the pure crystallized product. The pure acid may be dissolved in 230 parts of water, and used as a gargle, or in 25 parts of water for painting the throat, or in 50 parts for the carbolic-spray. By this process it becomes sufficiently deodorized for toilet purposes.