3. (J. J. Pohl.) Cane sugar is heated in a spacious metallic vessel by means of an oil bath to 410° or 419° Fahr. as long as aqueous vapours escape, the mass being occasionally stirred with a spatula. The mass is then finely powdered and digested with alcohol for two or three hours; the digestion is repeated until the fluid no longer tastes bitter.
Prop. A solution containing 10% of purified caramel is gummy, and forms a tremulous jelly on standing. Evaporated in vacuo, it dries up into a black shining mass soluble in water; but if the solution be evaporated to dryness by the heat of a water bath, the whole matter is rendered insoluble in hot or cold water. A very small proportion of caramel suffices to give a rich sepia tint to water.
CAR′AT. A weight of 4 grains used in weighing diamonds, which are spoken of as of so many carats weight. Among assayers, a carat is a weight of 12 grains; but more commonly a proportional weight or term, representing the number of parts of pure gold in 24 parts of the alloy; pure gold being spoken of as of 24 carats fine. It is commonly the 24th part of the “assay pound,” and is nominally subdivided into 4 assay grains, and these again into quarters. See Assaying.
CAR′AWAY. Syn. Caraway seed; Se′mena carui, L.; Carui, B. P. The fruit of the Carum Carui (Linn.), an umbelliferous plant, common in England and other parts of Europe. These fruits, commonly called “seeds,” form an agreeable and useful aromatic and carminative, and are especially esteemed in the flatulent colic of children. They are also largely employed as an adjuvant or corrective in various officinal preparations; and as a flavoring ingredient in cakes, biscuits, cordials, confectionery, &c. See Essences.
CARBAZOT′IC ACID. See Picric Acid.
CARBOL′IC ACID. H.C6H5O. Syn. Phenylic acid, Phenic acid, Phenol, Phenylic alcohol, Hydrate of phenyle, Hydrated oxide of phenyle. A powerful antiseptic substance obtained from coal-tar oil.
Prep. Crude, heavy coal oil is agitated with milk of lime, allowed to stand, and the aqueous portion separated from the undissolved oil and decomposed by hydrochloric acid. The oily liquid obtained is purified by distillation.
1. Crude coal oil is distilled in a retort furnished with a thermometer, and the portion which passes over when the heat ranges between 300° and 400° Fahr., is collected apart, and mixed with a hot saturated solution of caustic potassa; after standing for some time, a semi crystalline pasty mass forms, from which the supernatant liquid is decanted; the pasty mass is now agitated with a small quantity of water until dissolved; the solution thus formed separates into two portions, the denser of which contains carbolate of potassa; this being separated by decantation, is decomposed by hydrochloric acid. The solution of carbolic acid which rises to the surface is digested with chloride of calcium, to remove water, and purified by distillation; the distillate, by refrigeration, furnishes crystals of the acid, which must be drained, dried, and preserved from the air.
2. From salicylic acid. Mix intimately together equal weights of salicylic acid and powdered glass; introduce the mixture into a good German retort, and heat on a sand bath, gradually raising the heat till it becomes red hot at the bottom. The vapour is condensed in any convenient receiver. If the materials are perfectly dry, it solidifies to a mass of crystals as soon as it condenses, but if there be a trace of water present it remains liquid. The slower it distils over the lighter will be the colour, while if a high temperature be employed it comes over nearly black. It may be rendered colourless and anhydrous by rectification over quick-lime.
Of late years the manufacture of carbolic acid has increased to a great extent, and is generally found in a pale yellow clear solution, instead of as a dark hazy liquid. The pure anhydrous acid is in long, colourless, prismatic crystals, often, however, on keeping turning a beautiful pink, rose, or crimson, and which rapidly deliquesce in moist air, becoming converted into a colourless refractive liquid, having a faint odour of roses and tar. At 95° F. they become an oily liquid, having an odour and taste like creosote. Sp. gr. 1·065, boiling point 370° F. Exposed to the air the crystals absorb moisture and liquefy. The acid is slightly soluble in water, but freely soluble in glycerin, alcohol, and ether. Carbolic acid is poisonous, and is a powerful antiseptic.