water; when cold, the fat acid is separated, by use of a wet filter if necessary, and washed with water; and the water solution and washings exhausted with chloroform. The chloroform may be distilled from the phenic acid, and if necessary the distillation repeated. 36. NITROPHENIC ACID. HCH,(NO,),O. (Trinitrophenic acid.) Trinitrophenol. Carbazotic acid. Picric acid.Identified by its physical properties, especially its intense coloring effects (a); its precipitation of alkaloids (b); its reactions with special reagents (c).—Separated from water solutions by extraction with chloroform, etc. (a); by crystallization as a potassium salt (d).-Determined as salt of einchonia (e). a. In bright yellow crystalline scales or in octahedrons of the trimetric system. It melts when slowly heated and afterward sublimes; when quickly heated it explodes. It has a very bitter and somewhat acrid and sour taste, and when heated a suffocating odor and effect. It reddens litmus. It is soluble in 100 parts of water at 15° C. (59° F.) and in 25 parts at 80° C. (176° F.), less soluble in water acidulated with mineral acids, and freely soluble in alcohol, ether, chloroform, benzole, petroleum naphtha, and amylic alcohol. These solvents, which are not miscible with water, remove nitrophenic acid from water by aid of acidulation with sulphuric acid. The solutions have a yellow color, perceptible when very dilute; except solutions in benzole, petroleum naphtha, and dilute sulphuric acid, which are colorless. The colorless as well as colored solutions stain white paper, and more permanently stain the skin and fabrics of nitrogenous composition. The normal metallic picrates are all soluble in water, that of potassium being one of the least soluble, and requiring 260 parts of cold or 14 parts of boiling water for solution. This salt is insoluble in alcohol.-Many of the picrates explode more violently than the free acid, and oxidizable agents in intimate contact facilitate explosion, which may occur by trituration or pressure. b. Solution of salts of most of the alkaloids precipitate nitrophenic acid or its soluble salts-the cinchona alkaloids, the opium alkaloids, except morphia and pseudomorphia, the strychnos alkaloids, veratria, berberina, colchicia, and delphinia, being fully precipitated from solution even when dilute and well acidulated with sulphuric acid. Morphia is precipitated from moderately concentrated solutions having little or no free acid. The preci pitates are yellow, and are dissolved by hydrochloric acid. Compare 135, e. c. With ammoniacal cupric sulphate solution, nitrophenic acid forms a green precipitate.-Potassic cyanide, or potassic sulphide, or grape sugar, with nitrophenic acid and excess of potassa, in hot solution, gives a blood-red solution (yellow when greatly diluted) from formation of isopurpurate of potassium (the crystals of which are green by reflected light).-If ferrous sulphate is boiled in solution with nitrophenic acid, treated with excess of ammonia and filtered, the filtrate concentrated and acidulated with acetic acid, bright-red crystals of picramic acid are formed. Stannous chloride and several other reducing agents may be substituted for the ferrous salt. Picramic acid is nearly insoluble in water, but soluble in alcohol or ether. d. The graded solubility of potassic nitrophenate in hot and cold water and in alcohol (a) enables this salt to be almost perfectly removed from solution, in beautiful crystals, by gradual cooling of the hot water solution, with gradual addition of alcohol after crystallization has ceased in the cold water. Quantitative.-e. Nitrophenic acid or a soluble salt of this acid is precipitated by a solution of sulphate of cinchonia acidulated with sulphuric acid, the precipitate is washed with water, dried at a very gentle warmth, then heated (and melted) on the water-bath and weighed. C,H,N, (C.H‚[NO,],0), : 2HC‚¤ ̧ (NO),0 :: 1:0.6123. 37. SULPHOPHENIC ACID. HCH.SO. Phenyl sulphuric acid. Sulphophenylic acid. Sulphocarbolic acid.-Only preserved in its salts, which are stable and crystallizable compounds, decomposed by nitric acid with the formation of nitrophenic acids (35, b), and very gradually decomposed by boiling in solution with formation of sulphates and phenic acid.* Free sulphophenic acid evolves phenic acid when heated to the boiling point of the latter.-The sulphophenates are all soluble in water, and mostly soluble in alcohol. LIQUID NON-VOLATILE ACID. 38. LACTIC ACID. ECHO. Characterized by its physical properties (a); by the solubility and crystalline form of its salts (b); by the extent of its reducing power (c).Separated from many acids by the solubility of its lead salt in water, alcohol, and ether (d); from glycerin, sugar, etc., by the insolubility of its zinc salt in alcohol (f); from tissues, etc., as below (e).-Determined by saturation with alkali (g); by weight of zinc or magnesium salt (h). a. Absolute lactic acid is a colorless, odorless, syrupy liquid, of a very acid taste. Pure, it has the spec. grav. 1.248; when 75 per cent., the spec. grav. 1.212. Not volatile without decomposition; not decomposed by heat below 130° C.; at 145° C. vaporizes dilactic acid, at higher temperature lactide, both of which are converted to lactates by the alkalies.-Soluble in all proportions of water, alcohol, and ether; slightly soluble in chloroform. (Glyceric acid, C,H,O,, which resembles lactic acid, is insoluble in ether.) Concentrated sulphuric acid mixes with lactic acid without blackening it. Heated on platinum foil, it leaves a slight carbon residue which burns wholly away. PRESCOTT: Chem. News, xxvi., 269. b. The metallic lactates are all soluble in water; being mostly sparingly soluble in cold, freely in boiling water. Calcium lactate is soluble in 91 parts (sarcolactate in 12 parts) of cold water, soluble in alcohol, not in ether. Barium lactate is soluble in water and alcohol, insoluble in ether. Zinc lactate is soluble in 58 parts of cold, 6 parts of boiling water; insoluble in alcohol (sarcolactate in 6 parts cold water and in 2.2 parts cold alcohol). Silver lactate is soluble in water and in hot alcohol. Lead lactate is freely soluble in water, sparingly soluble in cold, readily in hot alcohol, slightly soluble in ether. (Glycerate of lead is but slightly soluble in cold water.) Calcium lactate (saturated with base) crystallizes in small white mammillated tufts, seen under the microscope to consist of delicate needles, some of which resemble a bundle of bristles bound midway between the ends. The acid lactate of calcium (supersaturated with acid) forms white hemispheres, compactly made of radiate needles, trimetric. Zinc lactate crystallizes from concentrated solutions in shining crusts, from dilute solutions in four-sided prismatic needles; the crystals, Zn(C,H,O,).. 3,0, lose their water rapidly at 100° C., and the salt decomposes above 210° C. (Zinc Sarcolactate crystallizes in slender needles, Zn(C,H ̧0,),.2H2O, losing their crystal water very slowly at 100° and giving off empyreumatic vapors below 150°.) Silver lactate crystallizes from neutral solutions, in slender needles, grouped in nodules, quickly blackening in the light. c. Lactic acid does not reduce the alkaline solution of sulphate of copper, but quickly reduces potassium permanganate from acid or alkaline solutions. d. Lactic acid may be separated from acids which form insoluble lead salts (and other insoluble bodies), according to the general method given at 40, g, either in alcoholic or aqueous solution. In a similar manner it is removed from insoluble barium salts, as soluble barium lactate, after saturation with carbonate of barium. The barium is then removed from the filtrate by precipitation with sulphuric acid and filtration, and the sulphuric acid is removed from the lactic acid in the last filtrate by repeatedly adding a mixture of 1 part of alcohol and 5 parts of ether and evaporating. e. Also, the fluid obtained by digestion and expression of tissues may be treated with sulphuric acid to fix albuminous matters, filtered, treated with alcohol and five times its weight of ether and again evaporated, filtering when necessary, till the sulphuric acid is removed. f. A (weighed) quantity of the material containing lactic acid, mixed with substances soluble in alcohol, is saturated in aqueous solution with oxide of zinc, the mixture evaporated to dryness, the residue digested in alcohol and filtered. The filtrate will contain the substances soluble in alcohol; the residue will contain zinc lactate, soluble in water. Quantitative.-g. In the acidimetry of lactic acid, onetenth equivalent, 9.000 being taken, the required number of cubic centimeters of normal solution of alkali equals the number per cent. of HC,H,O,. h. Saturating with oxide of zinc or oxide of magnesium, filtering and washing with water, crystallizing or evaporating, and drying at 100° C.: Mg(C,H,O,), 2нC,H ̧0,:: 1: 0.8911. LIQUID VOLATILE ACIDS. 39. FORMIC ACID. HCHO,. Identified by its odor (a); by its reducing power upon salts of the noble metals, permanganates, chromates, etc.—the radical CHO, being oxidized to HO and CO,―(b); by the color of its ferric salt in solution (c); by the odor of its ethyl salt (d).—Separated from substances less |