that of the whole mixture, is added. The precipitate is washed on the filter with 63 per cent. alcohol, and dried at a moderate heat. The citrate of barium contains a variable quantity of water, and is transformed into sulphate of barium by transferring to a porcelain capsule, burning the filter, and heating with sulphuric acid several times, till the weight is constant. 3BaSO: 2H ̧CH ̧0, . н,0 :: 1:0.601.

Hager directs that barium or calcium citrate (washed with alcohol) be dried at 120° to 150° and weighed. Ba,(C,H,O,),: 2H,CH,O,. H,O:: 1:0.53232.

9. ACONITIC ACID. H,CH,O,. A colorless solid, crystallizing with difficulty in warty masses, at 160° C. (320° F.) resolved into liquid itaconic acid. Soluble in water, alcohol, and ether; its solutions having a decided acid reaction. It has a purely acid taste. The aconitates of the alkaline metals, magnesium, and zinc are freely soluble, the others insoluble or sparingly soluble, in water. Calcic aconitate is soluble in about 100 parts of cold water and in a much smaller quantity of boiling water. Manganous aconitate crystallizes in rose-colored octahedrons, sparingly soluble in water. Argentic aconitate is sparingly soluble in water, soluble in alcohol or ether, blackened by boiling with water.-Free aconitic acid is precipitated by mercurous nitrate, but not by most metallic salts until after neutralization.

Aconitic acid is separated from Monkshood (Aconitum napellus), Larkspur (Delphinium consolida), Equisetum, Black Hellebore, Yarrow (Achillea millefolium), and other plants, in which it exists as calcium salt, by evaporating the clear decoction to crystallize. The crystals of aconitate of calcium are dissolved and precipitated by acetate of lead, and the lead salt decomposed by hydrosulphuric acid. It is also separated from impurities by adding (to the dry mixture) five parts of absolute alcohol, then saturating the filtered solution with hydrochloric acid, and adding water, when aconitate of ethyl will rise as an

oily layer, colorless and of aromatic odor.

decomposed by potassa.

This ether may be

Aconitic acid may be separated from Maleic acid by the more ready crystallization of the latter, and from Fumaric acid. by being more soluble in water.

10. MALIC ACID. H,CH,O,. Identified more especially by its deportment when heated (a); by the deportment of its lead salt when heated under water (b), and of its calcium salt in water and in alcohol (d).—Separated from tartaric, citric, oxalic, and other acids by alcoholic solubility of the neutral malate of ammonium (c) and by its reaction with calcium in water solutions (d); from tannic acid, also, by aqueous solubility of calcic malate, and from formic, acetic, benzoic acids by alcoholic insolubility of calcic malate (d).-Determined gravimetrically as lead malate (e).

Crystallizes in four-sided or six-sided prisms, deliquescent in air; colorless, odorless, and of sour taste; freely soluble in water and alcohol, soluble in ether. The malates are mostly soluble in water, but insoluble in alcohol. Nitric acid oxidizes malic acid, and alkaline solution of permanganate is decolorized by it, but chromic acid acts on it with difficulty. Malate of silver darkens but slightly on boiling (Tartrate blackens). Concentrated sulphuric acid darkens malic acid very slowly after warming. Hydriodic acid changes it to succinic acid with separation of iodine (the result being the same with Tartaric acid). Sodium amalgam changes malic to succinic acid.

a. Free malic acid, heated in a small retort over an oil-bath to 175° or 180° C., evolves vapors of maleic and fumaric acids, which crystallize in the retort and receiver. The fumaric acid forms slowly at 150° C., and mostly crystallizes in the retort, in broad, colorless, rhombic or hexagonal prisms, which vaporize without melting at about 200° C., and are soluble in 250 parts of water, easily soluble in alcohol or ether. If the temperature is suddenly raised to 200°, the maleic acid is the chief product.

Maleic acid crystallizes in oblique, rhomboidal prisms, which melt at 130° and vaporize at about 160°, and are readily soluble in water and in alcohol. The test for malic acid, by heating to 175° or 180°, may be made in a test-tube, with a sand-bath, the sublimate of fumaric and maleic acids condensing in the upper part of the tube. Malic acid melts below 100°, and does not lose weight at 120°; at the temperature of the test water-vapor is separated-maleic and fumaric acids both having the composition of malic anhydride (CHO).

b. Solution of acetate of lead precipitates malic acid, more perfectly after neutralizing with ammonia, as a white and frequently crystalline precipitate which upon a little boiling melts to a transparent, waxy semi-liquid (a characteristic reaction, obscured by presence of other salts). The precipitate is very sparingly soluble in cold water, somewhat soluble in hot water (distinction from Citrate and Tartrate); soluble in strong ammonia, but not readily dissolved in slight excess of ammonia (distinction from citrate and tartrate); slightly soluble in acetic acid.

c. If the precipitate of malate of lead is treated with excess of ammonia, dried on the water bath, triturated and moistened with alcoholic ammonia, and then treated with absolute alcohol, only the malate of ammonium dissolves (distinction from Tartaric, Citric, Oxalic, and many other organic acids, the normal ammonium salts of which are insoluble in absolute alcohol). Also, malic acid may be separated from tartaric, oxalic, and citric acids, in solution, by adding ammonia in slight excess, and then 8 or 9 volumes of alcohol, which leaves only the malate of ammonium in solution.

d. Solution of chloride of calcium does not precipitate malic acid or malates in the cold (distinction from Oxalic and Tartaric acids); only in neutral and very concentrated solutions is a precipitate formed on boiling (while calcic citrate is precipitated in neutral boiling solutions if not very dilute). The addition of alcohol after chloride of calcium produces a white bulky precipi

tate of calcic malate in even dilute neutral solutions (indicative in absence of sulphuric and other acids whose calcium salts are less soluble in alcohol than in water).—Acetic, Formic, and Benzoic acids are left in solution and malic acid precipitated by addition of one or two volumes of alcohol, with chloride of calcium. In separation from Tannic acid, both acids may be precipitated by chloride of calcium, with a slight excess of ammonia and alcohol; the malate is then washed out of the precipitate with water.

Quantitative.-e. The alcoholic solution of malate of ammonium-prepared as directed in c-may be precipitated with acetate of lead, washed with alcohol, dried and weighed as malate of lead. PbCHO, H,CH,O,::1: 0.3953.

: 5

11. MECONIC ACID. H,C,HO,. Identified by its physical properties and precipitation by hydrochloric acid (a); its reactions with iron and other metals (b); and by its products when heated (c). It is separated from opium through formation of the calcium salt or lead salt (ɗ).

a. Meconic acid crystallizes in white shining scales or small rhombic prisms, containing three molecules of crystallization water, fully given off at 100° C. It is soluble in 115 parts of water at ordinary temperatures, less soluble in water acidulated with hydrochloric acid, more soluble in hot water, freely soluble in alcohol, slightly soluble in ether. It has an acid and astringent taste and a marked acid reaction. Its salts, having two atoms of its hydrogen displaced by acid, are neutral to test-paper. Except those of the alkali metals, the dimetallic and trimetallic meconates are mostly insoluble in water. Meconates are nearly all insoluble in alcohol. They are but slightly or not at all decomposed by acetic acid.

Solutions of meconates are precipitated by hydrochloric acid, as explained above.

b. Solution of meconic acid is colored red by solution of ferric chloride. One ten-thousandth of a grain of the acid in

one grain of water with a drop of the reagent acquires a distinct purplish-red color (WORMLEY). The color is not readily discharged by addition of dilute hydrochloric acid (distinction from Acetic acid), or by solution of mercuric chloride (distinction from sulphocyanic acid).—Solution of acetate of lead precipitates meconic acid or meconates as the yellowish-white meconate of lead, Pb,(C,HO,),, insoluble in water or acetic acid.-Excess of baryta water precipitates a yellow trimetallic meconate.Solution of nitrate of silver in excess precipitates free meconic acid on boiling, and precipitates meconates directly, as yellow trimetallic meconate; if free meconic acid is in excess, the precipitate is first the white dimetallic meconate; both meconates being soluble in ammonia and insoluble in acetic acid.-Solution of chloride of calcium precipitates from solutions of meconic acid, and even from neutral meconates, chiefly the white monometallic meconate, CaH (C,HO,), 2H,O, sparingly soluble in cold water; in the presence of free ammonia, the less soluble, yellow dimetallic salt, CaH C,HO,. H2O, is formed. Both precipitates are soluble in about 20 parts of water acidulated with hydrochloric acid.

c. At 120° C. (248° F.) dry meconic acid is resolved into comenic acid; at above 200° C. the comenic acid is resolved into pyrocomenic acid and other products. The sublimate of comenic acid dissolves sparingly in hot water, not at all in absolute alcohol. It crystallizes in prisms, plates, or granules. Solution of comenic acid gives a red color with ferric chloride, green pyramidal crystals with cupric sulphate in concentrated solution, and a yellowish-white granular precipitate with acetate of lead.

d. The separation of meconic acid from opium is effected with least loss by precipitating the infusion with acetate. of lead (leaving the alkaloids as acetates with some excess of lead in the filtrate). The precipitate is decomposed, in water, with hydrosulphuric acid gas, and the filtrate therefrom is concentrated (and acidulated with hydrochloric acid) to crystallize the meconic acid.