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Hematein, C16H12O6—300.26—Prepared from logwood extract or from hematoxylin by treatment with ammonia and exposure to air. Reddish-brown crystals with a yellowish-green metallic luster. Very slightly soluble in water (about 1 in 1700); slightly soluble in alcohol and in ether; insoluble in benzene and in chloroform; freely soluble in diluted ammonia solution to form a solution of dusky purplish red color and in an aqueous solution of sodium hydroxide (1 in 50), to form a solution of bright red color, viewed in each case through a layer 1 cm in depth. Melts at a temperature above 200 and tends to decompose at 250.

Hematoxylin (Hydroxybrasilin), C16H14O6.3H2O—356.32—A crystalline substance derived from the heart-wood of Haematoxylon campechianum Linné (Fam. Leguminosae). Colorless to yellow prisms. Very slightly soluble in cold water and in ether; rapidly soluble in hot water and in hot alcohol. When exposed to light, it acquires a red color and yields a yellow solution. Dissolves in ammonia TS and in solutions of alkali hydroxides and carbonates. When dissolved in solutions of the following salts, it develops the colors indicated: in alum solution a red color; in stannous chloride solution a rose color; in solutions of cupric salts a greenish-gray color. It gradually turns black in potassium dichromate solution. Store hematoxylin and its solutions protected from light and air.

Hemoglobin, Bovine— [9008-02-0]—Use a suitable grade.
[NOTE—A suitable grade is available as Bovine Hemoglobin substrate powder from Sigma-Aldrich, www.sigma-aldrich.com.]

1-Heptadecanol, C17H36O—256.48 [1454-85-9]—Use a suitable grade.

Heptafluorobutyric Acid, C4F7O2H—214.04 [375-22-4]—Use a suitable grade.

Heptakis-(2,6-di-O-methyl)--cyclodextrin (2,6-Di-O-methyl--cyclodextrin; Dimethyl--cyclodextrin) C56H98O35— 1331.36[51166-71-3]—Use a suitable grade.

n-Heptane —Use n-Heptane, Chromatographic.
Change to read:

n-Heptane, Chromatographic —Clear, colorless, volatile, flammable liquid consisting essentially of C7H16. USP29 Practically insoluble in water; soluble in absolute alcohol. Miscible with ether, with chloroform, with benzene, and with most fixed and volatile oils.
NOTE—n-Heptane may require purification by passage through a column of silica gel, a ratio of about 25 g of the gel for each 100 mL of n-heptane being used, and subsequent fractional distillation.
Boiling range (Reagent test): between 94.5 and 99.0.
Spectral purity— Measure in a 1-cm cell at 250 nm, with a suitable spectrophotometer, against water as the blank: its absorbance is not more than 0.10.
Residue on evaporation— It meets the requirements of the test for Residue on evaporation under Hexane, Solvent.

Hexadecyl Hexadecanoate (Hexadecyl Palmitate; Cetyl Palmitate), C32H64O2—480.85—Use a suitable grade.
[NOTE—Suitable grades are available commercially as Hexadecyl Palmitate, and Palmitic Acid Palmityl Ester from Sigma-Aldrich, www.sigma-aldrich.com and Cetyl Palmitate, Catalog number C1203, from Spectrum Chemical Mfg. Corp., www.spectrumchemical.com.]
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Hexamethyldisilazane, C6H19NSi2—161.39—Clear, colorless liquid. USP29
Assay— When examined by gas–liquid chromatography, it shows a purity of not less than 95%. The following conditions have been found suitable for assaying the article: A 2-mm × 1.8-m glass column packed with phase G3 on support S1. Helium, flowing at a rate of about 40 mL per minute, is the carrier gas; the detector temperature is about 310; the injection port temperature is about 100; and the column temperature is programmed to start at 35, hold for 5 minutes, then rise at a rate of 8 per minute to 200. A flame-ionization detector is employed.
Residue after evaporation— Transfer 200 g to a tared dish, and evaporate on a steam bath to dryness. Dry the residue at 105 for 1 hour, cool, and weigh: not more than 0.0025% of residue is found.

Hexamethyleneimine (Homopiperidine), C6H12NH—99.17— Colorless to nearly colorless liquid.
Refractive index 831 : between 1.4640 and 1.4660 at 20.

n-Hexane, C6H14—86.18 (for use in spectrophotometry)—Use Hexanes.
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Hexane, Solvent (Petroleum Benzin; Petroleum Ether, Ligroin) —Clear, volatile liquid. USP29 Practically insoluble in water; soluble in absolute alcohol. Miscible with ether, with chloroform, with benzene, and with most fixed and volatile oils.
Caution—It is dangerously flammable. Keep it away from flames, and store in tight containers in a cool place.
Use ACS reagent grade Petroleum Ether.

Hexane, Solvent, Chromatographic— Use ACS HPLC reagent grade.

Hexanes (suitable for use in UV spectrophotometry); usually a mixture of several isomers of hexane (C6H14), predominantly n-hexane, and methylcyclopentane (C6H12)—Use ACS spectrophotometric reagent grade.

Hexanitrodiphenylamine (Dipicrylamine), C12H5N7O12—439.21—Yellow-gold powder or prisms. Explosive. Usually contains about 15% of water as a safety precaution. Insoluble in water, in alcohol, in acetone, and in ether; soluble in glacial acetic acid and in alkalies.
Water, Method I 921 : not more than 16%.

Hexanophenone, C12H16O—176.25—Yellow liquid.
Assay— Inject an appropriate specimen into a suitable gas chromatograph (see Chromatography 621) equipped with a flame-ionization detector, helium being used as the carrier gas. The following conditions have been found suitable: a 0.25-mm × 30-m capillary column coated with a 1-µm layer of phase G3; the injection port temperature is maintained at 280; the detector temperature is maintained at 300; the column temperature is maintained at 180 and programmed to rise 10 per minute to 280. The area of the C12H16O peak is not less than 98% of the total peak area.
Refractive index 831: 1.511 ± 0.002 at 20.

Histamine Dihydrochloride, C5H9N3·2HCl—184.07—Use USP Histamine Dihydrochloride RS.

L-Histidine Hydrochloride Monohydrate, C6H9N3O2·HCl·H2O—209.63[5934-29-2]—Use a suitable grade.

Horseradish Peroxidase Conjugated to Goat Anti-Mouse IgG— Affinity purified polyclonal antibody to Mouse Immune globulin (IgG) heavy and light chains (whole IgG) produced in Goat and labeled with horseradish peroxidase. Available either as a lyophilized powder or as a solution in a suitable buffer, generally 10 mM sodium phosphate, pH 7.4, containing a suitable preservative, such as 0.01% thimerosal, and an inactive protein(s) to prevent adsorption on the surface of the container. Use a suitable grade. Store at –20.

Hydrazine Hydrate, 85% in Water, (NH2)2·H2O—50.06—Colorless liquid.
Assay— Transfer 600 mg, accurately weighed, to a 100-mL volumetric flask. Dilute with water to volume, and mix. Pipet 10 mL into a suitable beaker, add 1.0 g of sodium bicarbonate and 50.0 mL of 0.1 N iodine VS. Titrate the excess iodine with 0.1 N sodium thiosulfate VS, using starch TS as the indicator. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N iodine is equivalent to 12.52 mg of (NH2)2·H2O. Not less than 83% is found.

Hydrazine Dihydrochloride, (NH2)2·2HCl—104.97—White powder.
Assay— Dissolve about 34 mg, accurately weighed, in 50 mL of water. Add carefully while stirring, 1 g of sodium bicarbonate. [Caution—There may be a rapid evolution of carbon dioxide. ] Titrate with 0.1 N iodine solution, determining the endpoint potentiometrically. Perform a blank determination, and make any necessary corrections. Each mL of 0.1 N iodine solution is equivalent to 2.63 mg of (NH2)2·2HCl. Not less than 98% is found.

Hydrazine Sulfate, (NH2)2·H2SO4—130.12[10034-93-2]—Use ACS reagent grade. [Caution—Great care should be taken in handling hydrazine sulfate because it is a suspected carcinogen. ]

Hydrindantin (2,2¢-Dihydroxy-2,2¢-biindan-1,1¢,3,3¢-tetrone), C18H10O6—322.27 [5103-42-4]—Sparingly soluble in hot water; soluble in methoxyethanol. When heated above 200, it becomes reddish brown.
Melting range 741: between 249 and 254.

Hydriodic Acid, HI—127.91—Use ACS reagent grade (containing not less than 47.0% of HI).
[NOTE—For methoxy determination (see Methoxy Determination 431), use hydriodic acid ACS reagent grade 55%. Use this grade also for alkoxyl determinations in assays in the individual monographs.]

Hydrochloric Acid, HCl—36.46—Use ACS reagent grade.

Hydrochloric Acid, Diluted (10 percent)—Prepare by mixing 226 mL of hydrochloric acid with sufficient water to make 1000 mL.

Hydrofluoric Acid, HF—20.01—Use ACS reagent grade.

Hydrogen Peroxide, 30 Percent, H2O2—34.01—Use ACS reagent grade.

Hydrogen Peroxide Solution —Use Hydrogen Peroxide Topical Solution.

Hydrogen Sulfide, H2S—34.08—Colorless, poisonous gas, heavier than air. Soluble in water. Is generated by treating ferrous sulfide with diluted sulfuric or diluted hydrochloric acid. Other sulfides yielding hydrogen sulfide with diluted acids may be used. Is also available in compressed form in cylinders.

Hydrogen Sulfide Detector Tube— A fuse-sealed glass tube so designed that gas may be passed through it and containing suitable absorbing filters and support media for the indicator, the latter consisting of a suitable lead salt.
Measuring range: 1 to 20 ppm.
[NOTE—Available from Draeger Safety, Inc., www.draeger.com, or from Gastec Corp., www.gastec.co.jp, distributed in the USA by www.nextteq.com.]

Hydroquinone, C6H4(OH)2—110.11—Fine, colorless or white, needle crystals. Darkens on exposure to air and light. Soluble in water, in alcohol, and in ether.
Assay— Accurately weigh about 250 mg, and dissolve in a mixture of 100 mL of water and 10 mL of 0.1 N sulfuric acid in a 250-mL conical flask. Add 3 drops of a 1 in 100 solution of diphenylamine in sulfuric acid, and titrate with 0.1 N ceric sulfate VS until the solution is red-violet in color. Each mL of 0.1 N ceric sulfate is equivalent to 5.506 mg of C6H4(OH)2. Not less than 99% is found.
Melting range 741: between 172 and 174.

3¢-Hydroxyacetophenone, C8H8O2—136.15—Light brown powder chips and chunks. Melts at about 96. Sparingly soluble in chloroform, yielding a clear, light yellow solution.
Assay— Inject an appropriate specimen into a suitable gas chromatograph (see Chromatography 621) equipped with a flame-ionization detector, helium being used as the carrier gas. The following conditions have been found suitable: a 0.25-mm × 30-m capillary column coated with G1; the detector and the injection port temperature are maintained at 300; the column temperature is maintained at 180 and programmed to rise 10 per minute to 280 and held at that temperature for 10 minutes. The area of the main peak is not less than 97% of the total peak area.

4¢-Hydroxyacetophenone, HOC6H4COCH3—136.15—Gray powder, melting at about 109.

p-Hydroxybenzoic Acid, C7H6O3—138.12—White crystals.
Assay— Transfer about 700 mg, accurately weighed, to a suitable container, and dissolve in 50 mL of acetone. Add 100 mL of water, mix, and titrate with 0.5 N sodium hydroxide VS, determining the endpoint potentiometrically. Perform a blank determination, and make any necessary correction. Each mL of 0.5 N sodium hydroxide is equivalent to 69.06 mg of C7H6O3: not less than 97% is found.
Melting range 741 : over a range of 2 that includes 216.

4-Hydroxybenzoic Acid Isopropyl Ester, HOC6H4COOCH(CH2)2—180.18—Use a suitable grade.
[NOTE—A suitable grade is available from TCI America, www.tciamerica.com.]
Melting range 741: between 84 and 87.

1-Hydroxybenzotriazole Hydrate, C6H5N3O·xH2O—135.13 (anhydrous)—White, crystalline powder. Sparingly soluble in alcohol yielding a clear, pale yellow solution.

2-Hydroxybenzyl Alcohol, C7H8O2—124.14—Off-white flakes. Very soluble in alcohol, in chloroform, and in ether; soluble in 15 parts water and in benzene.
Assay— Inject an appropriate specimen into a gas chromatograph (see Chromatography 621), equipped with a flame-ionization detector, helium being used as the carrier gas. The following conditions have been found suitable: a 0.25-mm × 30-m capillary column coated with a 1-µm layer of phase G2; the injection port temperature is maintained at 250; the detector temperature is maintained at 300; and the column temperature is maintained at 150 and programmed to rise 10 per minute to 280. The area of the C7H8O2 peak is not less than 99% of the total peak area.
Melting range 741: between 83 and 85.

N-(2-Hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid), C8H18N2O4S—238.3[7365-45-9]—Use a suitable grade.

4-Hydroxyisophthalic Acid, C8H6O4—182.13—Colorless branched needles. Freely soluble in alcohol and in ether.
Melting range 741 : between 308 and 310, with decomposition at 314 to 315.

Hydroxylamine Hydrochloride, NH2OH·HCl—69.49—Use ACS reagent grade.

Hydroxy Naphthol Blue (1-(2-Naphtholazo-3,6-disulfonic Acid)-2-naphthol-4-sulfonic acid, disodium salt), C20H12N2O11S3Na2—598.50—Deposited on crystals of sodium chloride in the concentration of about 1%. Use ACS reagent grade.

10-Hydroxynorandrostenedione (10-Hydroxy-19-norandrost-4-ene-3,17-dione), C18H24O3—288.38—Use a suitable grade.

3-Hydroxyphenyldimethylethyl Ammonium Chloride [Dimethylethyl(3-hydroxyphenyl)ammonium Chloride]—Use Edrophonium Chloride.

D--4-Hydroxyphenylglycine, C8H9NO3—167.16—Shiny leaflets. Sparingly soluble in water, in alcohol, in acetone, in ether, in chloroform, in ethyl acetate, in benzene, and in glacial acetic acid; soluble in alkalies and in mineral acids; freely soluble in warm 20% v/v hydrochloric acid.
Melting range 741 : between 220 and 247, with decomposition.

4-(4-Hydroxyphenyl)-2-butanone, C10H12O2—164.20—White powder.
Assay— Inject an appropriate volume into a gas chromatograph (see Chromatography 621) equipped with a flame-ionization detector, helium being used as the carrier gas. The following conditions have been found suitable: a 0.25-mm × 30-m capillary column coated with a 1-µm layer of phase G43; the injection port temperature is maintained at 280; the detector temperature is maintained at 300; the column temperature is maintained at 180 and programmed to rise 10 per minute to 280. The area of the C10H12O2 peak is not less than 98.5% of the total peak area.
Melting range 741: between 81 and 87.

2¢-(4-Hydroxyphenyl)-5-(4-methyl-1-piperazinyl)-2,5¢-bi-1H-benzimidazole Trihydrochloride Pentahydrate —623.97[23491-44-3]—Dark yellow to tan powder with a green cast. Use a suitable grade.

8-Hydroxyquinoline (Oxine), C9H7NO—145.16—Use ACS reagent grade 8-Quinolinol.

Hypophosphorous Acid, 50 Percent (Hypophosphorous Acid), HPH2O2—66.00—A colorless to faintly yellow liquid. Miscible with water and with alcohol.
Assay— Accurately weigh about 4 mL, dilute with 25 mL of water, add methyl red TS, and titrate with 1 N sodium hydroxide VS: each mL of 1 N sodium hydroxide is equivalent to 66.00 mg of HPH2O2. Not less than 48% is found.
Chloride— Add 0.2 mL to a mixture of 10 mL of silver nitrate TS and 5 mL of nitric acid, and heat until brown fumes are no longer evolved: any white, insoluble residue remaining is negligible.
Phosphate— Dilute 1 mL with water to 50 mL, render alkaline with ammonia TS, filter if a precipitate is formed, and add to the filtrate 5 mL of magnesia mixture TS: not more than a slight precipitate is formed within 5 minutes.
Sulfate (Reagent test, Method I)— Dilute 1 mL with water to 50 mL: 20 mL of the solution shows not more than 0.2 mg of SO4.

Hypoxanthine, C5H4N4O—136.11[68-94-0]—White to yellowish-white powder. Soluble in 1 N sodium hydroxide. Use a suitable grade.