Page:The New International Encyclopædia 1st ed. v. 04.djvu/231

* CARBOHYDRATES. 191 CARBOLIC ACID. clear. The saccharoses may, accordingly, be defined as follows: they are optically active chemical comiJounds, containing several hydro.xyl j;roups (OH), and one carbonyl group (CO) next to one of the hydroxyl groups ; some are al- dehydes (aldoses), others arc ketones (ketoses). They are capable of existing in numerous optical- ly isomeric forms, and a large number of them have been prepared artificially, after the possi- bility of their existence hud been indicated by the theories of stereo-chemistry (q.v. ), al- though many of these isomers are imknown to exist ready-formed anywhere in nature. The Di-saccuaroses. These include ordioary cane-sugar, milk-sugar, maltose, etc., and are composed of two molecules of some one saccha- rose, or of some two different saccharoses. Their chemical nature is, however, as yet imperfectly understood. By the action of dilute acids, or by certain processes of fermentation, the di-saccha- rcses may be broken up into saccharoses, but yeast has no direct action on them. Unlike the saccharoses, the di-saceharoses have no reducing effect on Febling's solution. The formula CnH^Ou represents the composition of any one of the di- saccharoses. The Poly-sacchakoses. These include starch, cellulose, etc., and are chemically very complex, and as yet very little understood. Like the di-saceharoses, they have no effect on Febling's solution, and yeast has no direct action on them. The composition of the poly-saccharoses is usually represented by the general formula (CsHjoOs)^. The carbohydrates are among the most neces- sary constituents of food. Their presence has been shown to be indispensable to the forma- tion of fats, and their own value as sources of muscular energy, though smaller than that of fats, is still very considerable. The value and uses of the most important car- bohydrates are discussed in this Encyclop.'Edia under their special names. See Cellulose; Dextrix ; Gluten ; Starch ; Sugars ; Food ; etc. CARBOLIC (carbon + ol + ic) ACID, Phemc .crD. or Phenol. CV.HsOH. An important organic substance largely used as an antiseptic, disinfectant, and deodorant, as well as in the manufacture of certain dyes. It is formed when various organic substances are strongly heated, and is, therefore, found in the tar produced by the destructive distillation of coal, wood, shale, etc. The chief material from which it is made on an industrial scale is the tar obtained in the manufacture of coal-gas. Carbolic acid is ex- tracted from the fraction of coal-tar which dis- tils over between the temperatures 170° and 2.30° C. This portion, called middle oil, or car- bolic oil, is treated with a solution of caustic Boda, which combines all the phenol, but at the same time takes up a certain amoimt of the hy- drocarbons contained in the oil. The hydrocar- bons are driven off by a current of steam passed through the alkaline solution, and then the still impure sodium salt of phenol is decomposed with dilute sulphuric acid, and the crude phenol thus obtained is rectified in wrought-iron stills. The fraction passing over between 17.5° and 205° is subjected to further fractional distillation, the final product being practically pure phenol. At ordinary temperatures pure phenol is solid, crys- tallizing in large, colorless prismatic crystals that melt at 42° C. The melting-point is, how- ever, considerably lowered by the pressure of minute quantities of water. The boiling-point of pure phenol is 183° C. If exposed to tlie action of the air, carbolic acid gradually assumes a red coloration, which is said to be caused by the presence of minute traces of lead; a permanently colorless phenol may be obtained by oxidizing, the impurity with a little potassium perman- ganate and sulphuric acid. Carbolic acid mixes in all proportions with alcohol, other, chloro- form, glycerin, olive oil, and other organic liquids. It is but sparingly soluble in water, which is itself soluble in phenol only to a lim- ited extent, hen water is shaken with phenol in such relative quantities that tlie limits of solubility are exceeded, the mixture separates into two liquid layers, the upper being a solu- tion of phenol in water, the lower a solution of water in phenol. Weak aqueous .solutions of phenol are sometimes used as a gargle, and by adding a few drops of essence of peppermint a pleasant and efficient mouth-wash may be ob- tained. The aqueous solutions have a sweetish taste, and leave, as an aftertaste, a slightly burning sensation in the moutii. Solutions of phenol in oil have no antiseptic properties. Car- bolic acid is sometimes administered internally — of course in small doses. It may also be i:sed to relieve toothache. Carbolic acid has the pe- culiar effect of rendering the urine dark, even though but a small quantity should enter the body by absorption from surgical dressings. Taken internally in somewhat concentrated form carbolic acid acts rapidly as a poison, produc- ing collapse, a cold and clammy skin, feeble res- piration, etc. The mouth, throat, oesophagus, and stomach exhibit white eschars, or sloughs. In cases of poisoning, an emetic should be ad- ministered, followed by a dilute solution of mag- nesium or sodium sulphate taken intenially; soluble sulphates combine with carbolic acid to form the harmless sulpho-carbolates, such as sodium sulpho-carbolate, CjHj.OH.NaSO,. It is also necessary to inject some stimulant, for in- stance, brandy, subcutaneously Carbolic acid may be readily detected in a substance submit- ted for analysis by dissolving some of the sub- stance in water and adding a drop of ferric chloride solution: in the presence of carbolic acid a violet color is produced. The following, however, is a much more sensitive test: Phenol combines directly with bromine to fonu tri- brom-phenol bromide, a yellowish-white solid compound: to test a solution for phenol, bromine water may, therefore, be added, when, if mere traces of phenol are present, a flocculent pre- cipitate will form either immediately or on standing for a short time. The bromine reaction is also used for the quantitative determination of phenol. Carbolic acid was discovered in 1834 by Runge, among the products obtained in the distillation of coal-tar. A few years later Lau- rent succeeded in preparing a nure crystalline carbolic acid which he analyzed and named phenic acid, or phenyl hydrate, from the Greek ipahciv — to give light. The commercial product known as crude carbolic arid contains, I>eside3 phenol, various other substances derived from coal-tar: it has a creosote-like odor, and is com- posed chiefly of phenol and cresol. Formerly carbolic acid was much used in sur- gery for protecting the part operated upon from