Naphthalene, C10H8—128.17 [91-20-3]—Monoclinic prismatic plates, or white scales or powder. Use a suitable grade with a content of not less than 98%.

1,3-Naphthalenediol (Naphthoresorcinol), C10H6(OH)2—160.17 [132-86-5]—Grayish-white to tan crystals or powder. Freely soluble in methanol; sparingly soluble in water, in alcohol, and in ether.
Melting range 741: between 122 and 127.
Solubility in methanol— Dissolve 500 mg in 50 mL of methanol: the solution is clear and complete.

2,7-Naphthalenediol (2,7-Dihydroxynaphthalene), C10H8O2—160.17 [582-17-2]—Off-white to yellow, crystalline solid or powder. Dissolves in acetone.
Melting range 741: between 187 and 191.

2-Naphthalenesulfonic Acid, C10H8O3S·H2O—226.25 [120-18-3]—Off-white to light gray crystals. Soluble in water.
Assay— Dissolve about 1 g, accurately weighed, in 100 mL of water, add phenolphthalein TS, and titrate with 0.1 N sodium hydroxide VS. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N sodium hydroxide is equivalent to 22.63 mg of C10H8O3S·H2O. Not less than 98.0% is found.
Melting range 741 : between 122 and 126, but the range between beginning and end of melting does not exceed 2.

1-Naphthol (Alphanaphthol), C10H7OH—144.17 [90-15-3]—Colorless or slightly pinkish crystals or crystalline powder.

2-Naphthol (Betanaphthol), C10H7OH—144.17 [135-19-3]—White leaflets or crystalline powder. Discolors on exposure to light. Very slightly soluble in water; soluble in alcohol, in ether, in chloroform, and in solutions of alkali hydroxides.
Melting range 741: between 121 and 123.
Solubility in alcohol— A solution of 1 g in 10 mL of alcohol is complete and colorless or practically so.
Residue on ignition (Reagent test): not more than 0.05%.
Acidity— Shake 1 g with 50 mL of water occasionally during 15 minutes, and filter: the filtrate is neutral to litmus.
1-Naphthol— Boil 100 mg with 10 mL of water until dissolved, cool, and filter. Add to the filtrate 0.3 mL of 1 N sodium hydroxide and 0.3 mL of 0.1 N iodine: no violet color is produced.
Insoluble in ammonia (naphthalene, etc.)— Shake 500 mg with 30 mL of ammonia TS: the 2-naphthol dissolves completely and the solution is not darker than pale yellow.

Naphthol Dipotassium Disulfonate (2-Naphthol-6,8-dipotassium Disulfonate), C10H6K2O7S2—380.48 [842-18-2]—Use a suitable grade.
[Note—A suitable grade is available as “2-naphthyl-6,8-disulfonic acid dipotassium salt” from Pfaltz and Bauer, Inc., www.pfaltzandbauer.com. ]

Naphthol Disodium Disulfonate (2-Naphthol-3,6-disodium Disulfonate), C10H6Na2O7S2—348.26—Use a suitable grade.

p-Naphtholbenzein, C27H18O2—374.43 [145-50-6]—Red-brown powder. Use a suitable grade.

-Naphthoquinone-4-sodium Sulfonate, C10H5NaO5S—260.20—Yellow to orange-yellow crystals or crystalline powder. Soluble in about 10 parts of water; insoluble in alcohol.
Loss on drying 731— Dry it in vacuum at about 50: it loses not more than 2.0% of its weight.
Residue on ignition (Reagent test)— Ignite 1 g of dried sample with 3 mL of sulfuric acid: the residue weighs between 265 and 280 mg (between 26.5% and 28.0%).

Naphthoresorcinol (1,3-Dihydroresorcinol), C10H8O2—160.17 [132-86-5]—Use a suitable grade.

2-Naphthyl Chloroformate (Chloroformic Acid 2-Naphthyl Ester), ClCOOC10H7—206.62 [7693-50-7]—Use a suitable grade.
[Note—A suitable grade is available from TCI America, www.tciamerica.com. ]

1-Naphthylamine, C10H9N—143.19 [134-32-7]—Use a suitable grade.

1-Naphthylamine Hydrochloride, C10H7NH2·HCl—179.65 [552-46-5]—White, crystalline powder that turns bluish upon exposure to light and air. Soluble in water, in alcohol, and in ether.
A 1 in 100 solution, make slightly acid with acetic acid, gives a violet color with 5 drops of ferric chloride TS. A 1 in 40 solution in diluted acetic acid is colorless and not more than slightly opalescent.
Residue on ignition (Reagent test)— Ignite 200 mg with a few drops of sulfuric acid: the weight of the residue is negligible.

N-(1-Naphthyl)ethylenediamine Dihydrochloride, C10H7NH(CH2)2NH2·2HCl—259.17 [1465-25-4]—Use ACS reagent grade.

Neutralized Alcohol —See Alcohol, Neutralized.

Nickel, Ni—58.6934 [7440-02-0]—Use a suitable grade.

Nickel-Aluminum Catalyst —Use a suitable grade.
[Note—A suitable grade is “Raney Nickel, Active Catalyst,” available as “aluminum–nickel alloy,” catalog number 72240, available from Fluka Chemical Corp., fax 1-800-962-9591, Web site: www.sigma-aldrich.com. ]

Nickel Sulfate, NiSO4·6H2O—262.85 [7786-81-4]—Use ACS reagent grade.

Nickel (II) Sulfate Heptahydrate, NiSO4·7H2O—280.9 [10101-98-1]—Use a suitable grade.

Change to read:
-Nicotinamide Adenine Dinucleotide, C21H27N7O14P2—663.4 [53-84-9]—White, very hygroscopic powder. Freely soluble in water. Use a suitable grade with a content of NLT 98%.USP38

Nicotinamide Adenine Dinucleotide Phosphate-adenosine-5¢-triphosphate Mixture —Use a suitable grade.
Suitability— When used in the assay of lactulose, determine that a suitable absorbance-versus-concentration slope is obtained, using USP Lactulose RS , the reagent blank absorbance being not more than 0.020. The commercially available reagent contains 64 mg of nicotinamide adenine dinucleotide phosphate and 160 mg of adenosine-5¢-triphosphate per vial. The mixture is buffered and stabilized. For use in the Assay of lactulose it is diluted with water to 100 mL.

Nicotinic Acid —Use Niacin (USP monograph).

Ninhydrin, C9H4O3·H2O—178.14 [485-47-2]—Use ACS reagent grade.

Nitric Acid, HNO3—63.01 [7697-37-2]—Use ACS reagent grade.

Nitric Acid, Diluted, HNO3[7697-37-2]—Dilute 143 mL of nitric acid with water to 1000 mL.

Nitric Acid, Fuming (90 Percent Nitric Acid), HNO3—63.01 [7697-37-2]—Use ACS reagent grade Nitric Acid, 90 Percent.

Nitric Acid, Lead-Free— Use ACS reagent grade.
Lead— To 100 g add 0.1 g of anhydrous sodium carbonate and evaporate to dryness. Dissolve the residue in water, heating slightly, and dilute with the same solvent to 50.0 mL. Determine the lead content by atomic absorption spectrophotometry (see Spectrophotometry and Light-Scattering 851) measuring the absorbance at 283.3 nm or 217.0 nm using a lead hollow-cathode lamp and an air–acetylene flame. It contains not more than 0.1 ppm of lead (Pb).

Nitric Oxide–Nitrogen Dioxide 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 an oxidizing layer and the indicator diphenyl benzidine.
Measuring range: 0.5 to 10 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. ]

Nitrilotriacetic Acid, N(CH2COOH)3—191.14 [139-13-9]—Use ACS reagent grade.

5-Nitro-1,10-phenanthroline, C12H7N3O2—225.20 [4199-88-6]—White powder. Soluble in water.
Melting range 741: between 198 and 200.
Suitability as redox indicator— Dissolve 25 mg in a minimum volume of diluted sulfuric acid, add 10 mg of ferrous sulfate, and dilute with water to 100 mL: the solution is deep red in color and exhibits an absorption maximum at 510 nm. To 1.0 mL of the solution add 1.0 mL of 0.01 M ceric sulfate: the red color is discharged.

4¢-Nitroacetophenone (p¢-Nitroacetophenone), C8H7NO3—165.15 [100-19-6]—Yellow crystals.
Assay— Inject an appropriate ether solution of the specimen (about 0.5 µL) into a suitable gas chromatograph (see Chromatography 621) equipped with a thermal conductivity detector, helium being used as the carrier gas. The following conditions have been found suitable: a 4-mm × 1.8-m stainless steel column containing 10% phase G1 on support S1A; the injection port and detector temperatures are maintained at 200 and 300, respectively; the column temperature is maintained at 170 and programmed to rise 3 per minute to 220. The area of the 4¢-nitroacetophenone peak is not less than 97% of the total peak area.
Melting range 741: between 78 and 80.

o-Nitroaniline, NO2C6H4NH2—138.12 [88-74-4]—Orange-yellow crystals. Slightly soluble in cold water; soluble in hot water; freely soluble in alcohol and in chloroform. It forms water-soluble salts with mineral acids.
Melting range 741: between 71 and 72.

p-Nitroaniline, NO2C6H4NH2—138.12 [100-01-6]—Bright yellow, crystalline powder. Insoluble in water; soluble in alcohol and in ether.
Melting range 741: between 146 and 148.
Solubility— Separate 1-g portions dissolve in 30 mL of alcohol and in 40 mL of ether, respectively, to yield solutions that are clear or practically so.
Residue on ignition (Reagent test): not more than 0.2%.

Nitrobenzene, C6H5NO2—123.11 [98-95-3]—Use ACS reagent grade.

p-Nitrobenzenediazonium Tetrafluoroborate, NO2C6H4N2BF4—236.92 [456-27-9]—Yellow-gold crystals. Soluble in acetonitrile. [Caution—Shock-sensitive; keep refrigerated. ]
Assay— Transfer about 30 mg, accurately weighed, to a low-actinic, 100-mL volumetric flask. Dissolve in 0.01 N hydrochloric acid, dilute with 0.01 N hydrochloric acid to volume, and mix. Using low-actinic glassware, dilute 2.0 mL of the resulting solution with spectrophotometric grade methanol to 50.0 mL. Measure the absorbance of this solution in a 1-cm cell at about 255 nm, using methanol as the blank. Calculate the absorptivity of the solution by dividing the measured absorbance by the concentration in g per mL. Calculate the assay value by the formula:
100a/59.4
 in which a is the absorptivity of the solution: not less than 95.0% is found.

Add the following:
4-Nitrobenzoic Acid (p-Nitrobenzoic Acid), C7H5NO4—167.12[ 62-23-7]—Use a suitable grade with a content of NLT 98%.1S (USP38)

p-Nitrobenzyl Bromide, NO2C6H4CH2Br—216.03—Almost white to pale yellow crystals, darkening on exposure to light. Practically insoluble in water; freely soluble in alcohol, in ether, and in glacial acetic acid. Store in tight, light-resistant containers.
Melting range 741: between 98 and 100.
Solubility— Separate 200-mg portions yield clear solutions in 5 mL of alcohol and in 5 mL of glacial acetic acid.
Residue on ignition (Reagent test): negligible, from 200 mg.

4-(p-Nitrobenzyl)pyridine, C12H10N2O2—214.22[1083-48-3]—Yellow crystals. Soluble in acetone.
Use a suitable grade with a content of not less than 98%.

Nitrogen Certified Standard —A suitable NLT 99.99% nitrogen certified standard is available from most suppliers of specialty gases.

Nitromethane, CH3NO2—61.04 [75-52-5]—Use ACS reagent grade.

Nitroso R Salt (1-Nitroso-2-naphthol-3,6-disodium Disulfonate), NOC10H4OH(SO3Na)2—377.26 [525-05-3]—Yellow crystals or crystalline powder. One g dissolves in about 40 mL of water; insoluble in alcohol.
Sensitiveness— Dissolve 500 mg of sodium acetate in a solution of 0.4 mg of cobaltous chloride (0.1 mg of cobalt) in 5 mL of water. Add 1 mL of diluted acetic acid, and follow with 1 mL of a solution of the nitroso R salt (1 in 500): a red color, which is produced at once, persists when the solution is boiled with 1 mL of hydrochloric acid for 1 minute.

1-Nitroso-2-naphthol, C10H7NO2—173.17 [131-91-9]—Brown to yellowish-brown powder. Insoluble in water; soluble in alcohol, in benzene, in ether, in carbon tetrachloride, and in acetic acid.
Assay— Transfer about 250 mg, previously dried over silica gel to constant weight and accurately weighed, to a glass-stoppered flask, and dissolve in 10 mL of sodium hydroxide solution (1 in 10). Cool the solution in an ice bath, add dilute sulfuric acid (1 in 6) until a slight, permanent precipitate is formed and the solution is slightly acid, then add 3 g of potassium iodide, shake to dissolve, add 20 mL of dilute sulfuric acid (1 in 6), immediately insert the stopper in the flask, and allow to stand in the dark for 2 hours. Titrate the liberated iodine with 0.1 N sodium thiosulfate VS, adding 3 mL of starch TS as the endpoint is approached. Perform a complete blank determination, and make any necessary correction. Each mL of 0.1 N sodium thiosulfate is equivalent to 8.66 mg of C10H7NO2: not less than 95.0% is found.
Melting range 741: between 109 and 111.
Residue on ignition (Reagent test): not more than 0.2%.

Nitrous Oxide Certified Standard [10024-97-2]—A container of 99.9% nitrous oxide. It is available from most suppliers of specialty gases.

Nonadecane, C19H40—268.52 [629-92-5]—White solid.
Assay— Inject an appropriate specimen into a suitable gas chromatograph (see Chromatography 621) equipped with a thermal conductivity detector, helium being used as the carrier gas. The following conditions have been found suitable: 3-mm × 1.8-m stainless steel column containing 5% phase G2 on support S1AB; the injection port temperature is maintained at 330; the detector temperature is maintained at 300; and the oven temperature is held initially at 190 and allowed to rise gradually to 250. The area of the nonadecane peak is not less than 99% of the total peak area.
Melting range 741: between 31.5 and 33.5.

Nonanoic Acid, C9H18O2—158.24 [112-05-0]—Clear, colorless to faint yellow liquid. Miscible with water and with methanol.
Assay— Accurately weigh about 500 mg, transfer to a suitable container, add 30 mL of water, and mix. Add 40 mL of water, and mix. Add phenolphthalein TS, and titrate with 0.1 N sodium hydroxide VS. Each mL of 0.1 N sodium hydroxide is equivalent to 15.82 mg of C9H18O2: not less than 96.0% of C9H18O2 is found.
Refractive index 831: about 1.432 at 20.

Nonionic Wetting Agent— Use a suitable amphoteric surfactant.
[Note—A suitable grade is commercially available as Triton X-100 or Octoxynol 9. ]

Nonoxynol-9 (Igepal CO-630, Semicid, Staycept, Tergitol TP-9, Sterox), (C2H4O)nC15H24O—[26027-38-3]—Use a suitable grade.

1-Nonyl Alcohol (1-Nonanol), CH3(CH2)8OH—144.25[143-08-8]—Colorless liquid.
Assay— Not less than 97% of C9H20O is found, a suitable gas chromatograph equipped with a flame-ionization detector and helium being used as the carrier gas at a flow rate of about 40 mL per minute. The following conditions have been found suitable: a 3.2-mm × 1.83-m stainless steel column packed with 20% phase G16 on support S1A; the injection port, column, and detector temperatures are maintained at about 250, 160, and 310, respectively.
Refractive index 831: between 1.432 and 1.434 at 20.

n-Nonylamine (1-Aminononane), C9H21N—143.27 [112-20-9]—Use a suitable grade.

Nonylphenol Polyoxyethylene Ether, (CH3)3CCH2C(CH3)2CH2C6H4O(CH2CH2O)XH, where x is approximately 40 to 1900–2100[9016-45-9]—White solid; melts at approximately 44. Use a suitable grade.

Nonylphenoxypoly(ethyleneoxy)ethanol —Clear, viscous, pale yellow liquid. May exhibit slight solidification on cooling; warming with agitation will restore to original condition. Density: about 1.06. Soluble in alcohol, in xylene, and in water. Suitable for use in gas–liquid chromatography.
[Note—A suitable grade is “Igepal CO 710,” available from General Aniline and Film Corp., 140 West 51st St., New York, NY 10020. ]

Normal Butyl Alcohol —See Butyl Alcohol.

Normal Butylamine —See n-Butylamine.

Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Reagent Margareth R. C. Marques, Ph.D.
Senior Scientific Liaison
(301) 816-8106		 (HDQ) Headquarters