Naphthalene,
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1,3-Naphthalenediol
(Naphthoresorcinol),
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Melting range
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Solubility in methanol—
Dissolve 500 mg in 50 mL of methanol: the solution is clear and complete.
2,7-Naphthalenediol
(2,7-Dihydroxynaphthalene),
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Melting range
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2-Naphthalenesulfonic Acid,
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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
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1-Naphthol
(Alphanaphthol),
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2-Naphthol
(Betanaphthol),
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Melting range
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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),
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[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),
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p-Naphtholbenzein,
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Loss on drying
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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),
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2-Naphthyl Chloroformate
(Chloroformic Acid 2-Naphthyl Ester),
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[Note—A suitable grade is available from TCI America, www.tciamerica.com. ]
1-Naphthylamine,
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1-Naphthylamine Hydrochloride,
![]() ![]() ![]() ![]() 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,
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Nickel,
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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,
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Nickel (II) Sulfate Heptahydrate,
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Change to read:
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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,
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Nitric Acid,
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Nitric Acid, Diluted,
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Nitric Acid, Fuming
(90 Percent Nitric Acid),
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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
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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,
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5-Nitro-1,10-phenanthroline,
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Melting range
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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),
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Assay—
Inject an appropriate ether solution of the specimen (about 0.5 µL) into a suitable gas chromatograph (see Chromatography
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Melting range
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o-Nitroaniline,
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Melting range
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p-Nitroaniline,
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Melting range
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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,
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p-Nitrobenzenediazonium Tetrafluoroborate,
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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:
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p-Nitrobenzyl Bromide,
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Melting range
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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):
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4-(p-Nitrobenzyl)pyridine,
![]() ![]() ![]() ![]() 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,
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Nitroso R Salt
(1-Nitroso-2-naphthol-3,6-disodium Disulfonate),
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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,
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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
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Residue on ignition (Reagent test):
not more than 0.2%.
Nitrous Oxide Certified Standard
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Nonadecane,
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Assay—
Inject an appropriate specimen into a suitable gas chromatograph (see Chromatography
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Melting range
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Nonanoic Acid,
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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
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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),
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1-Nonyl Alcohol
(1-Nonanol),
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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
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Refractive index
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n-Nonylamine (1-Aminononane),
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Nonylphenol Polyoxyethylene Ether,
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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. ]
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
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