Home › Acids › To Obtain Carbolic Acid

To Obtain Carbolic Acid

This spray. By this process it becomes sufficiently is obtained from that portion of coal-tar deodorized for toilet purposes. which distills over between 300° and 400° 3920. Phosphoric Acid. This acid, in Fahr.; this, when mixed with a hot concen- its pure or anhydrous state, can only be ob trated solution of hydrate of potassa, is re- tained by the direct combination of its elcsolved, on the addition of water, into a light ments, phosphorus and oxygen, 1 equivalent oil and a heavier alkaline liquid. By separat- of phosphorus combining with 5 of oxygen. ing the latter, and neutralizing it with It consists of a white, flaky, extremely delimuriatic acid, impure carbolic acid will float quescent powder, which, when fused and on the surface in the form of a light oil. If cooled, assumes a vitreous appearance. It is this be 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 capable of assuming three separate conditions in combination with water as a base; the union of 1 equivalent of anhydrous acid with 1 equivalent of water produces monobasic or glacial phosphoric acid, called also metaphosphoric acid; 1 equivalent of anhydrous acid, with 2 of water, gives bibasic or pyrophosliquid carbolic acid. The introduction of a phoric acid; 1 of anhydrous acid with 3 of crystal of carbolic acid into the acid to be water forms tribasic, or commercial phoscongealed, greatly facilitates its crystallization.

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

Put 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. phoric acid. This last is the common form of the acid. These three forms of the acid are not pure phosphoric acid in different degrees of dilution, as they have distinguishing characteristics. Monobasic phosphoric acid coagulates albumen, and gives white gelatinous uncrystallizable precipitates with the soluble salts of baryta, lime, and silver; the bibasic does not coagulate albumen, and makes, when neutralized only, a white precipitate with nitrate of silver; the tribasic does not affect albumen, and, when neutralized, throws down a yellow precipitate (phosphate of silver) from nitrate of silver. Tribasic phosphoric acid is the usual form under which phosphoric acid combines with the bases to form PHOS- PHATES.