I. Tests, Reagents, Test Solutions, and

Volumetric Solutions

Introductory

Official Substances as Reagents. Some official substances (chemicals, chemical solutions, etc.) are sufficiently pure to be used as reagents, if they comply with the tests of purity prescribed by the Pharmacopoeia. Latin official names are not used as titles in the following list, the English name being preferred. In the case of non-official substances, the presence of certain impurities, though immaterial for their use as medicines, renders their employment as reagents unsuitable. Whenever a greater degree of purity is required than is provided for by the text of the Pharmacopoeia, it will be specially mentioned in the following lists.

Abbreviations and Signs Used:

T.S.Test Solution.

V.S. = Volumetric Solution.

Normal (see under "Volumetric Solutions' in List III).

N

2

N

; 50

Double-normal (sometimes written: 2N).

Fiftieth-normal;

Keeping of Reagents.-Reagents should be kept in bottles made of glass free from lead and arsenic, and not subject to corrosion by acids and alkalies.

The bottles should be closed by well-ground glass or rubber stoppers. Ground glass stoppers of bottles containing alkali hydroxides, ammonium sulphide, ammonia water, and other substances of alkaline reaction rapidly attacking ground glass surfaces, should be coated with a thin film of petrolatum.

Reagents easily affected by light, such as hydrogen sulphide T.S., ammonium sulphide T.S., chlorine water, silver nitrate T.S., etc., should be kept in bottles made of dark amber-colored glass.

NOTE.-As some of the following test solutions are in certain cases directed to be used in definite quantities in place of the regular volumetric solutions, it is important that they should always be prepared of the exact strength prescribed.

Tests, Reagents, and Test Solutions

NOTE. The reagents are arranged in alphabetical order. The test solutions are usually mentioned in connection with the principal chemical or other substance from which they are prepared. The volumetric solutions will be found on page 544.

Whenever water is required or mentioned as a solvent in the tests given in the Pharmacopoeia, or in the preparation of any reagent, it is understood that distilled water shall be used.

1. Absolute Alcohol.-Ethyl alcohol, C,H,OH.-Use the official absolute alcohol [Alcohol Absolutum, U. S. P.], which should be neutral to litmus T.S.

2. Acetic Acid, HC,H,O,.-Use the official acetic acid [Acidum Aceticum, U. S. P.].

3. Albumin Test Solution.-Carefully separate the white of a hen's egg (which should be fresh) from the yolk, shake it thoroughly with 100 Cc. of water, and filter. This solution should be freshly made when required.

4. Alcohol. Ethyl Alcohol, CH,OH.-Use the official alcohol [Alcohol, U. S. P.]. Alcohol of lower strength is prepared as follows:

Alcohol, 90 percent.-Mix 51 Cc. of alcohol [Alcohol, U. S. P.] with 3 Cc. of distilled water. The specific gravity of the mixture should be 0.826 at 25° C. (77° F.), corresponding to 90 percent., by volume, of absolute alcohol.

5. Alcohol, 80 percent.-Mix 45.5 Cc. of alcohol [Alcohol, U. S. P.] with 9.5 Cc. of distilled water. The specific gravity of the mixture should be 0.856 at 25° C. (77° F.), corresponding to 80 percent., by volume, of absolute alcohol.

6. Alcohol, 70 percent.-Mix 38.6 Cc. of alcohol [Alcohol, U. S. P.] with 15 Cc. of distilled water. The specific gravity of the mixture should be 0.882 at 25° C. (77° F.), corresponding to 70 percent., by volume, of absolute alcohol.

7. Ammonia Water, NH4OH.-Use the official ammonia water [Aqua Ammonia, U. S. P.].

8. Ammonium Carbonate Test Solution.-Dissolve 20 Gm. of ammonium carbonate, NH,HCO,. NHÂNH,CO2 [Ammonii Carbonas, U. S. P.], in a mixture of 20 Cc. of ammonia water and 70 Cc. of water, and add sufficient water to measure 100 Cc.

9. Ammonium Chloride Test Solution.-Dissolve 10 Gm. of ammonium chloride, NH4Cl [Ammonii Chloridum, U. S. P.], in sufficient water to measure 100 Cc.

10. Ammonium Molybdate Test Solution.-Dissolve 15 Gm. of finely powdered ammonium molybdate, (NH4) ̧M07O2 + 4H,O, in 100 Cc. of distilled water, adding sufficient ammonia water, if necessary, to effect solution. Then gradually pour the liquid into 100 Cc. of nitric acid (sp. gr. 1.403 at 25° C. [77° F.]). The resulting solution, after being subjected to gentle heat for about two hours, should be decanted from any yellow sediment which may be deposited.

Pour Solution No. 1 into Solution No. 2 gradually, shaking repeatedly. After being subjected to a gentle heat for about two hours, the solution should be decanted from any yellow sediment which may be deposited.

Preserve the test solution in the dark, and, if a sediment should form in it after some days, carefully decant the clear solution from it.

11. Ammonium Oxalate Test Solution.-Dissolve 4 Gm. of pure crystallized ammonium oxalate, (NH4)2C2O4 + H2O, in sufficient water to measure 100 Cc. Or, dissolve 4 Gm. of pure oxalic acid (see No. 73) in 100 Cc. of water, add 15 Cc. of ammonia water, to expel excess of ammonia, and dilute with water to 113 Cc.

boil

On evaporating a portion of the test solution, and igniting the residue, it should be completely volatilized (absence of fixed impurities). The precipitate produced by the addition of silver nitrate T.S., or by barium chloride T.S., should dissolve without residue upon the addition of nitric acid (absence of chlorides and sulphates).

12. Ammonium Sulphate, (NH4)2SO4.—This salt should respond to the following tests of purity: Three grammes should leave no appreciable residue upon ignition (absence of fixed impurities). The aqueous solution of the salt (1 in 10) should not respond to the TimeLimit Test for Heavy Metals (see No. 121). Another portion of this solution should not become turbid upon the addition of nitric acid and silver nitrate T.S. (absence of chlorides). Another portion of this solution should not be colored red upon the addition of 2 drops of hydrochloric acid and 1 drop of ferric chloride T.S. (absence of sulphocyanate). This salt may be prepared by neutralizing pure sulphuric acid, which has been diluted with an equal volume of water, with ammonia water, evaporating and crystallizing. During the evaporation, the solution should be tested from time to time with litmus paper, adding more ammonia if necessary to keep the liquid alkaline.

13. Ammonium Sulphide Test Solution.-Saturate 3 parts of pure ammonia water with hydrogen sulphide, prepared as directed (No. 47), and add to the solution (which now contains ammonium hydrogen sulphide, NH,HS) 2 parts of ammonia water, which converts the greater portion of the ammonium hydrogen sulphide into ammonium sulphide, (NH4)2S. The solution should be perfectly clear and colorless, and should leave no residue on evaporation. It should not be rendered turbid either by magnesium sulphate T.S. (absence of free ammonia), or by calcium chloride T.S. (absence of ammonium carbonate). It should be protected against air and light by being kept in small, dark amber-colored bottles, in a cool, dark place. As soon as a notable deposit of sulphur has made its appearance in the solution, it should be rejected.

Ammonium polysulphide test solution is occasionally required. It is a yellow liquid, made by dissolving a small quantity of pure sulphur in the preceding colorless ammonium sulphide test solution.

14. Amyl Alcohol, CH12OH.-A colorless, oily liquid having a penetrating characteristic odor, boiling at 131° C. (267.8° F.); soluble in 40 parts of water at 25° C. (77° F.); miscible with alcohol, ether, chloroform, carbon disulphide, petroleum benzin, benzene, and fixed and volatile oils.

15. Aniline (Phenylamine), C,H,NH,.-When freshly distilled, aniline is a colorless, strongly refractive, oily liquid having a peculiar aromatic odor and a pungent, burning taste. Upon exposure to the light and air, it rapidly assumes a reddish-brown color. Specific gravity 1.0214 at 25° C. (77° F.). Aniline should distil over com