test for free alkali or alkaline carbonate is made by adding mercuric chloride to the soap solution; a red-brown to redyellow precipitate indicates free alkali-the fat acid salts forming only white precipitates.

i. Then, for volumetric determination of the combined alkali of the soap, the soap precipitate is rinsed (with dilute solution of common salt) from the filter into a beaker, and decomposed by a five-times stronger than normal standard solution of (hydrochloric) acid, added to beginning of acid reaction. After which the fat acid may be separated as a cake and weighed, according to c—a weighed quantity of beeswax or paraffin being added, if necessary to secure solidification.

j. Determination of glycerin. Take 10 grams of soap, dissolve in alcohol, add alcoholic solution of sulphuric acid until precipitation ceases, and filter. Add baric carbonate and filter again. Evaporate until all the alcohol is expelled, and weigh the sweet residue as glycerin (SENIER). Or, treat the filtrate from acid precipitation of the fat acids with basic subacetate of lead, filter, remove the excess of lead by hydrosulphuric acid and filtration, neutralize with hydrochloric acid and extract with a mixture of alcohol 2 vols. and ether 1 vol. Evaporate this solvent and weigh as glycerin (VOHL).

k. A plan for determination of the constituents of soap, viz.: (1) Carbonates and other salts, color substances and foreign matters; (2) Free Alkali; (3) Combined Alkali; (4) Fatty acids with resin; (5) Fatty acids without resin; (6) Glycerin; (7) Water.*

For (1): Digest ten grams soap with alcohol (five or six ounces) on water-bath, filter and wash with hot alcohol in a hot funnel. Dry the residue at 100° C. and weigh. Analyze this residue by solution with water, by alkalimetry, etc.

For (2) Through the filtrate of (1) pass a stream of carbonic acid gas; if a precipitate forms, continue until its forma

* SENIER: "A Process," etc., Am. Jour. Phar., 1874, 353.

tion ceases; filter and wash and determine the alkali in the preci- · pitate by a volumetric solution of (oxalic) acid. (See h.)

For (3): The filtrate from (2)—or if there was no precipitate in (2), the filtrate from (1)—after the addition of about an ounce of water, is evaporated on the water-bath to expel all the alcohol, and the (combined) alkali therein determined (as Soda or Potassa) by adding a normal solution of oxalic acid to acid reaction. (Compare i.)

For (4): To the mixture left in (3) add a little sulphuric acid; then add ten grams of previously melted beeswax, heat on a water-bath to fuse the wax, cool, weigh the cake, and subtract the weight of the wax. (Compare c.)

For (5) Dissolve 40 grams of soap in water, decompose by dilute sulphuric acid, cool at temperature below 14° C., separate and weigh the fatty acids; then digest them for some time with a mixture of water with nearly as much alcohol, until the subsident liquid (when the mixture has cooled and the fatty acids again solidified) ceases to be milky. Weigh the fatty stratum again; subtract the previous weight, and divide by four-for the resin in 10 grams soap. (Compare g.)

For (6) Proceed according to the first method under j.

:

For (7) Estimate by difference; or by evaporation of another portion with alcohol and sand, as directed in a.

Vitreous and

68. RESINS. Compounds of C, H, and O. mostly brittle solids (when unmixed), softening and melting when gently heated, but not vaporizable (distinction from camphors); mostly heavier than water. The class includes some substances of pungent taste, some of poisonous effect, and some of intense color. Mostly insoluble or but slightly soluble in water: mostly soluble in absolute alcohol; by far the greater number soluble in ether and in benzole (means of separation from gums). Many resins are soluble in aqueous alkalies, by combination as resin-soaps; and in alcoholic solution show the acid reaction.

The resins of commerce include, first, vegetable exudates, of which the Resins proper mostly contain some extractive matters; the Gum-resins being mixtures with gums; the Oleo-resins, mixtures with volatile oils (including the source of common resin or colophony); and the Balsams, mixtures with volatile oils and acids formed by oxidation of volatile oils. Second, resins extracted from plants by alcohol, including some of both the Medicinal resins and the Color resins. And, third, resins obtained from liquid plant juices which are dried as a part of the manufacture; these including two bodies insoluble in alcohol, Caoutchouc and Indigo.

69. The separation of resins from volatile oils is effected by distillation with water; from gums, by fusion and straining at 100° C.; and from various bodies and from each other by action of the solvents applicable in the case. See Recapitulation, 99. Solution with alcohol and precipitation by pouring the solution into water is by far the most generally applicable process; solution with aqueous alkali and precipitation by acid may sometimes be employed.

70. THE RESINOUS MATTER OF ALOES is fusible on the waterbath; insoluble in cold water, partly soluble in boiling water, freely soluble in alcohol, partly soluble in ether, scarcely at all soluble in chloroform, benzole, naphtha, bisulphide of carbon, freely soluble in aqueous alkalies and in glycerin.—ALOES yields paracumaric acid, as follows: The hot ammoniacal water solution is precipitated with acetate of lead, the filtrate freed from lead by dilute sulphuric acid, and this second filtrate is boiled in presence of the (excess of) sulphuric acid-forming (from resin) paracumaric acid in solution. The latter colors ferric chloride dark gold-brown.-The residue from an ammoniacal solution of material containing aloes, when saturated with hydrochloric acid, yields the odor of aloes. Farther, see Aloin.

71. AMBER Resin. Amber contains Succinic acid, Volatile oil, and resin (two resins). Amber is a hard and brittle, more or less transparent solid, of spec. grav. 1.065; tasteless, aro

matic when rubbed or warmed, of various colors, chiefly yellow or orange. Subjected to gradually increasing heat, it softens; at 110° to 260° C., evolves a volatile oil colored blue by hydrochloric acid; at about 235° C., evolves succinic anhydride; at 287°, it fuses; at higher temperatures, yields first a colorless oil, then a yellowish wax.-Amber resin is insoluble in water, alcohol (except which is soft resin), ether, benzole, bisulphide of carbon, petroleum naphtha, volatile and fixed oils, but soluble in fixed alkalies (except a slight residue) and in concentrated sulphuric acid (with a red color).-Fuming nitric acid changes it to a nitrogenous resin of musk-like odor and gelatinous consistence" artificial musk."

72. AMMONIAC Resin. Ammoniac contains 72 per cent. resin and 22 per cent. gums, and a little volatile oil. Ammoniac is a solid, soft when warmed, brittle when cold, of specific gravity 1.207, whitish to yellow-brown and dirty gray, of a sweetishbitter and acrid taste and strong peculiar odor. Ammoniac is partly soluble in water, alcohol, ether, acetic acid, and aqueous alkalies. Ammoniac Resin is wholly soluble in alcohol, in fixed and volatile oils, in sulphuric acid, acetic acid, and aqueous alkalies, and partly soluble in ether.

73. ASSAFETIDA Resin. Assafetida contains over 60 per cent of resin, about 30 per cent. of gums, and about 4 per cent. of volatile oil (whereon its odor depends). Assafetida is a solid, soft when warm, and brittle when cold, of spec. grav. 1.327, having an intense fetid and alliaceous odor and a bitter, acrid, and persistent taste. Its color is variegated and altered, being on fresh surfaces whitish to yellowish, becoming reddish to yellow-brown on exposure.-The volatile oil is separated by distillation with water, contains sulphur, and boils at 140° C.Assafetida resin is readily soluble in alcohol, not wholly insoluble in water, nearly all soluble in ether, mostly soluble in alkalies.

74. BENZOIN Resins. Benzoin or 66 benzoin-gum " consists of about three-fourths part resins, 10 to 15 per cent. of Benzoic

acid, with a little gum and a very little volatile oil. Benzoin is a brittle solid, of spec. grav. above 1.062, melting and evolving benzoic acid when heated; of variegated colors, fragrant balsamic odor, and little taste, with slight acrid after-taste when chewed. Benzoin resins (three have been identified) are all soluble in alcohol, in concentrated sulphuric acid (from which water precipitates them violet), and in strong potassa solution, but insoluble in water. Resin-a is insoluble in aqueous carbonate of sodium, or in ammonia, but soluble in ether. Resin-b has the solubilities above given for a, except that it is insoluble in ether. Resin-c is sparingly soluble in ether and in volatile oils, and soluble in aqueous carbonate of sodium. The ether solution of c deposits a sediment which has been considered a fourth resin.-Dry distillation of benzoin, after removal of benzoic acid, gives a rose-red distillate.

75. CANAUBA WAX. Consists of myristic alcohol, resin, and other substance. It is a solid of spec. grav. 0.999, harder than beeswax, melting at 84° C., and of a greenish-yellow color. It is insoluble in water; dissolves with difficulty in alcohol, in ether, and in bisulphide of carbon; dissolves readily in oil of turpentine, but not at all in linseed oil, and not in aqueous alkalies. It is not changed by sulphuric acid, but is stained deep yellow by nitric acid.

76. CAOUTCHOUC. Fusible at 120° C. (248° F.); not vaporizable. The larger part soluble in ether, benzole, bisulphide of carbon, petroleum naphtha, or oil of turpentine; wholly soluble in chloroform, and in a mixture of 100 parts bisulphide of carbon with 6 or 8 parts of absolute alcohol. Sparingly soluble in hot amylic alcohol. Not acted upon by alcohol or aqueous alkalies; slowly decomposed by concentrated sulphuric or nitric acid.

77. COLOPHONY. Resin of Turpentine. Common Resin or Rosin. A pale-yellow to brownish-yellow, translucent, brittle, vitreous solid, of spec. grav. of 1.07 to 1.08; softening at 70° C. and melting at 135° C. At a higher temperature it suffers destructive distillation, forming "essence of rosin" and then