U.S. PHARMACOPEIA

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Magnesium, Mg—24.305—Silvery metal in ribbon form. Reacts slowly with water at room temperature. Dissolves readily in dilute acids with the liberation of hydrogen.
Assay— Transfer 1 g, accurately weighed, to a 250-mL volumetric flask, and dissolve in a mixture of 15 mL of hydrochloric acid and 85 mL of water. When solution is complete, dilute with water to volume, and mix. Pipet 25 mL of the dilution into a 400-mL beaker, dilute with water to 250 mL, add 20 mL of ammonia-ammonium chloride TS and a few mg of eriochrome black T trituration, and titrate with 0.1 M edetate disodium VS to a blue endpoint. Each mL of 0.1 M edetate disodium VS is equivalent to 2.430 mg of Mg. Not less than 99% is found.

Magnesium Acetate, Mg(C2H3O2)2·4H2O—214.45—Use ACS reagent grade.

Magnesium Chloride, MgCl2·6H2O—203.30—Use ACS reagent grade.

Magnesium Nitrate, Mg(NO3)2·6H2O—256.41—Use ACS reagent grade.

Magnesium Oxide, MgO—40.30—Use ACS reagent grade.

Magnesium Oxide, Chromatographic —Use a suitable grade.

Magnesium Perchlorate, Anhydrous, Mg(ClO4)2—223.21—Use ACS reagent grade.

Magnesium Silicate, Activated —Use a suitable grade.

Magnesium Silicate, Chromatographic —Extremely white, hard, powdered (60- to 100-mesh) magnesia–silica gel. Suitable for use as an adsorbant in column chromatography.

Magnesium Sulfate, MgSO4·7H2O—246.48—Use ACS reagent grade.

Magnesium Sulfate, Anhydrous, MgSO4—120.37—Anhydrous Magnesium Sulfate may be prepared as follows. Place a suitable quantity of magnesium sulfate (see above), preferably powdered, in a shallow vessel, and expose to a temperature of about 80 for several hours with occasional stirring. Then heat at 275 to 300 until the weight is practically constant. Transfer the product while still warm to tight containers, as the anhydrous salt is very hygroscopic.

Malachite Green G —See Brilliant Green.
Change to read:

Maleic Acid, C4H4O4—116.07—White, USP29 crystalline powder. Soluble in 1.5 parts of water, in 2 parts of alcohol, and in 12 parts of ether.
Assay— Dissolve about 2 g, accurately weighed, in 100 mL of water and titrate with 1 N sodium hydroxide VS, using phenolphthalein TS as the indicator. Each mL of 1 N sodium hydroxide is equivalent to 58.04 mg of C4H4O4: not less than 99% of C4H4O4, calculated on the dried basis, is found.
Loss on drying— Dry it in vacuum over phosphorus pentoxide for 2 hours: it loses not more than 1.5% of its weight.
Residue on ignition 281: not more than 0.1%.

Manganese Dioxide— See Manganese Dioxide, Activated.

Manganese Dioxide, Activated (Manganese (IV) Oxide, Activated), MnO2—86.94—Use a suitable grade.

Melamine (2,4,6-Triamino-1,3,5-triazine), C3H6N6—126.1[108-78-1]—Use a suitable grade.

2-Mercaptoethanol (-Mercaptoethanol), C2H6OS—78.13[60-24-2]—Use a suitable grade.

Mercuric Acetate, Hg(C2H3O2)2—318.68—Use ACS reagent grade.

Mercuric Bromide, HgBr2—360.40—Use ACS reagent grade.

Mercuric Chloride, HgCl2—271.50—Use ACS reagent grade.

Mercuric Iodide, Red, HgI2—454.40—Use ACS reagent grade.

Mercuric Nitrate, Hg(NO3)2·xH2O—342.62—Use ACS reagent grade. This reagent is available as either the mono- or dihydrate.

Mercurous Nitrate Dihydrate (Mercury (I) Nitrate Dihydrate), Hg2(NO3)2·2H2O—561.22—Use ACS reagent grade.

Mercuric Oxide, Yellow, HgO—216.59—Use ACS reagent grade.

Mercuric Sulfate, HgSO4—296.65—Use ACS reagent grade.

Mercuric Thiocyanate, Hg(SCN)2—316.76—White, crystalline powder. Very slightly soluble in water; soluble in solutions of sodium chloride; slightly soluble in alcohol and in ether.

Mercury, Hg—At. Wt. 200.59—Use ACS reagent grade.

Mesityl Oxide, C6H10O—98.14—Colorless 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 G2; the injection port temperature is maintained at 150; the detector temperature is maintained at 300; the column temperature is maintained at 50 and programmed to rise 10 per minute to 200. The area of the C6H10O peak is not less than 98% of the total peak area.
Refractive index 831: between 1.443 and 1.447 at 20.

Metaphenylenediamine Hydrochloride (Metaphenylenediamine Dihydrochloride), C6H4(NH2)2·2HCl—181.06—White or slightly reddish-white, crystalline powder. Easily soluble in water. On exposure to light it acquires a reddish color. Store it protected from light.
Solubility— A solution of 1 g in 200 mL of water is colorless.
Residue on ignition (Reagent test)— Ignite 1 g with 0.5 mL of sulfuric acid: the residue weighs not more than 1 mg (0.1%).
[NOTE—Metaphenylenediamine hydrochloride solution can be decolorized by treatment with a small quantity of activated charcoal.]

Metaphosphoric Acid (Vitreous Sodium Acid Metaphosphate), HPO3—79.98—Use ACS reagent grade.

Methacrylic Acid —Use a suitable grade.

Methacrylic Carboxylic Acid Cation-exchange Resin —See Cation-exchange Resin, Methacrylic Carboxylic Acid.

Methanesulfonic Acid, CH4O3S—96.11—Use a suitable grade.

Methanol (Methyl Alcohol), CH3OH—32.04—Use ACS reagent grade.

Methanol, Aldehyde-Free, CH3OH—32.04—Dissolve 25 g of iodine in 1 L of methanol and pour the solution, with constant stirring, into 400 mL of 1 N sodium hydroxide. Add 150 mL of water, and allow to stand for 16 hours. Filter, and boil under a reflux condenser until the odor of iodoform disappears. Distill the solution by fractional distillation. It contains not more than 0.001% of aldehydes and ketones.

Methanol, Anhydrous —Use Methanol.

Methanol, Spectrophotometric —Use ACS reagent grade Methanol Suitable for Use in UV Spectrophotometry.

Methenamine— Use Methenamine (USP monograph).

Methoxyethanol (Ethylene Glycol Monomethyl Ether; 2-Methoxyethanol), CH3OCH2CH2OH—76.09—Use ACS reagent grade.

2-Methoxyethanol (Ethylene Glycol Monomethyl Ether; Methoxyethanol), CH3OCH2CH2OH—76.09—See Methoxyethanol.

5-Methoxy-2-methyl-3-indoleacetic Acid, C12H13NO3—219.24—Off-white powder.
Assay— Transfer about 110 mg, accurately weighed, to a 100-mL beaker. Add 30 mL of methanol and dissolve by stirring. Add 40 mL of water, and mix. Titrate with 0.1 N sodium hydroxide VS, determining the endpoint potentiometrically. Perform a blank determination and make any necessary correction. Each mL of 0.1 N sodium hydroxide is equivalent to 21.92 mg of C12H13NO3. Not less than 98% is found.
Melting range 741 : between 161 and 168, but the range between beginning and end of melting does not exceed 3.

Methoxyphenylacetic Acid (-Methoxyphenylacetic Acid), C9H10O3—166.2 [1701-77-5]—Use a suitable grade.
Change to read:

Methyl Acetate, C3H6O2—74.08—Colorless liquid. USP29 Soluble in water. Miscible with alcohol and with ether.
Specific gravity 841: about 0.933.
Refractive index 831: between 1.3615 and 1.3625 at 20.
Boiling range (Reagent test)— Not less than 95% distills between 57 and 58.

Methyl 4-Aminobenzoate, C8H9NO2—151.16—Off-white powder.
Assay— Dissolve about 38 mg, accurately weighed, in 50 mL of glacial acetic acid. Titrate with 0.1 N perchloric acid VS, determining the endpoint potentiometrically. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 15.12 mg of C8H9NO2. Not less than 99.0% is found.
Melting range 741 : between 108 and 110.

Methyl Arachidate, C21H42O2—326.56—Off-white flakes.
Assay— Inject an appropriate specimen into a 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 2.0-mm × 1.8-m glass column packed with 5% G2 phase on support S1A; the injection port temperature is maintained at 300; the detector temperature is maintained at 300; the column temperature is maintained at 230 and programmed to rise 3 per minute to 280. The area of the C2H42O2 peak is not less than 99% of the total peak area.
Melting range 741: between 46 and 51.

Methyl Behenate, C23H46O2—354.61—White powder.
Assay— Inject an appropriate specimen into a 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 2.0-mm × 1.8-m glass column packed with 5% G3 phase on support S1A; the injection port temperature is maintained at 300; the detector temperature is maintained at 300; the initial temperature of the oven is 220, which is held for 2 minutes, and then programmed to rise 3 per minute to attain a final temperature of 270, which is held for 10 minutes. The area of the C23H46O2 peak is not less than 98% of the total peak area.
Melting range 741: between 54 and 56.

Methyl Benzenesulfonate, C7H8O3S—172.20 [80-18-2]—Use a suitable grade.

Methyl Caprate, C11H22O2—186.29—Colorless liquid.
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 G2; the injection port temperature is maintained at 250; the detector temperature is maintained at 300; the column temperature is maintained at 150 and programmed to rise 10 per minute to 280. The area of the C11H22O2 peak is not less than 98.5% of the total peak area.

Methyl Caprylate, C9H18O2—158.24—Colorless liquid.
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 G2; the injection port temperature is maintained at 230; the detector temperature is maintained at 300; the column temperature is maintained at 130 and programmed to rise 10 per minute to 280. The area of the C9H18O2 peak is not less than 98.5% of the total peak area.

Methyl Carbamate C2H5NO2—75.07—White crystals. Freely soluble in water.
Melting range 741: between 54 and 56.

Methyl Chloroform (Methylchloroform; 1,1,1-Trichloroethane), CH3CCl3—133.40—Use ACS reagent grade.

5,5¢-Methylenedisalicylic Acid (3,3¢-Methylene-bis[6-hydroxybenzoic Acid]), C15H12O6—288.25—Use a suitable grade.

Methyl Erucate, C23H44O2—352.59—Colorless liquid.

Methyl Ethyl Ketone, CH3COC2H5—72.11—Use ACS reagent grade 2-butanone.

Methyl Green, C27H35N3BrCl·ZnCl2—653.24[7114-03-6]—Use a suitable grade.

Methyl Heptadecanoate, C18H36O2—284.48—White, crystalline flakes.
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 G8; the injection port temperature is maintained at 220; the detector temperature is maintained at 220; the column temperature is maintained at 180 and programmed to rise 4 per minute to 220. The area of the C18H36O2 peak is not less than 99% of the total peak area.
Melting range 741: between 31 and 32.

Methyl Iodide, CH3I—141.94—Colorless, heavy, transparent liquid. Slightly soluble in water. Miscible with alcohol, with ether, and with solvent hexane. Turns brown on exposure to light as a result of liberation of iodine.
Assay— Add 1 mL to a 100-mL volumetric flask tared with 10 mL of alcohol. Weigh again, add alcohol to volume, and mix. Pipet 20 mL into a glass-stoppered flask, and add 50.0 mL of 0.1 N silver nitrate VS and 2 mL of nitric acid. Insert the stopper immediately, shake frequently during 2 hours, and allow to stand in the dark overnight. Shake again for 2 hours, then add 50 mL of water and 3 mL of ferric ammonium sulfate TS, and titrate the excess silver nitrate with 0.1 N ammonium thiocyanate VS. Each mL of 0.1 N silver nitrate is equivalent to 14.19 mg of CH3I: not less than 98.5% is found.
Boiling range (Reagent test)— Distill 50 mL into a chilled, partly closed receiver: not less than 48 mL distills between 41.5 and 43.
Density: between 2.270 and 2.285.
Residue on evaporation— Evaporate 4 mL (10 g) on a steam bath, and dry the residue at 105 for 1 hour: the residue weighs not more than 1 mg (0.01%).
Acidity— Shake 3 mL with 5 mL of water for 30 seconds, and immediately draw off the lower layer: the aqueous layer is neutral to litmus, and when 1 mL of silver nitrate TS is added, it shows not more than a slight opalescence.

Methyl Isobutyl Ketone —See 4-Methyl-2-pentanone.

Methyl Laurate, C13H26O2—214.34—Colorless liquid.
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 G2; 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 C13H26O2 peak is not less than 99.45% of the total peak area.

Methyl Lignocerate, C25H50O2—382.66—White crystals.

Methyl Linoleate, C19H34O2—294.47—Colorless liquid.
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 G2; the injection port temperature is maintained at 300; the detector temperature is maintained at 300; the column temperature is maintained at 200 and programmed to rise 10 per minute to 300. The area of the C19H34O2 peak is not less than 99% of the total peak area.

Methyl Linolenate, C19H32O2—292.46—Colorless liquid.
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 14% cyanopropylphenyl-86% dimethylpolysiloxane; 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 C19H32O3 peak is not less than 99% of the total peak area.
Refractive index 831: between 1.469 and 1.473 at 20.

Methyl Methacrylate —Use a suitable grade.

Methyl Myristate, C15H30O2—242.40—Colorless liquid.
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 G2; the injection port temperature is maintained at 300; the detector temperature is maintained at 300; the column temperature is maintained at 200 and programmed to rise 10 per minute to 300. The area of the C15H30O2 peak is not less than 99% of the total peak area.
Refractive index 831: between 1.434 and 1.438 at 20.

N-Methyl-N-nitroso-p-toluenesulfonamide (p-Tolylsulfonylmethylnitrosamide), C8H10N2O3S—214.24—Light yellow crystals or powder. Insoluble in water; soluble in benzene, in carbon tetrachloride, and in chloroform.
Melting range 741 : between 59 and 63, but the range between beginning and end of melting does not exceed 2.

Methyl Oleate, C19H36O2—296.49—Colorless 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 capillary column coated with a 1-µm layer of phase G2; the injection port temperature is maintained at 300; the detector temperature is maintained at 300; the column temperature is maintained at 230 and programmed to rise 10 per minute to 280. The area of the C19H36O2 peak is not less than 99% of the total peak area.
Refractive index 831: 1.452 at 20.

Methyl Palmitate, C17H34O2—270.45—White solid.
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 G2; the injection port temperature is maintained at 300; the detector temperature is maintained at 300; the column temperature is maintained at 200 and programmed to rise 10 per minute to 300. The area of the C17H34O2 peak is not less than 96.5% of the total peak area.

4-Methylpentan-2-ol, C6H14O—102.2—Use a suitable grade.
Add the following:

Methyl Red (2-[4-dimethylaminophenylazo]benzoic acid, C. I. Acid Red 2) C15H15N3O2—269.30—Use ACS reagent grade.USP29

Methyl Stearate, C19H38O2—298.50—Off-white, crystalline solid.
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 capillary column coated with a 1-µm layer of phase G2; the injection port temperature is maintained at 300; the detector temperature is maintained at 300; the column temperature is maintained 200 and programmed to rise 10 per minute to 300. The area of the C19H38O2 peak is not less than 99% of the total peak area.
Melting range 741: between 40 and 42.

Methyl Sulfoxide —See Dimethyl Sulfoxide.

Methylamine, 40 Percent in Water, CH5N—31.06—Colorless liquid.
Assay— Using a syringe, transfer about 0.5 mL of a well-shaken specimen to 100 mL of water at a point below the surface of the water. Determine the weight of the specimen by weighing the syringe before and after the transfer. Mix, and titrate with 0.5 N hydrochloric acid VS, determining the endpoint potentiometrically, using a silver-silver chloride pH electrode and a calomel reference electrode. Perform a blank determination, and make any necessary correction. Each mL of 0.5 N hydrochloric acid is equivalent to 15.53 mg of CH5N: between 39.0% and 41.0% is found.
Refractive index 831 : between 1.3680 and 1.3710, at 20.

p-Methylaminophenol Sulfate, (p-CH3NHC6H4OH)2·H2SO4—344.38—Use ACS reagent grade.

4-Methylbenzophenone, C14H12O—196.25[134-84-9]—Use a suitable grade.
Melting range 741 : between 56.5 and 57.

Methylbenzothiazolone Hydrazone Hydrochloride, C8H10CIN3S·H2O—233.7—An almost white or yellowish, crystalline powder.
Melting point 741: about 270.
Suitability for determination of adehydes— To 2 mL of aldehyde-free methanol add 60 µL of a 1 g per L solution of propionaldehyde in aldehyde-free methanol and 5 mL of a 4 g per L solution of methylbenzothiazolone hydrazone hydrochloride. Mix, and allow to stand for 30 minutes. Prepare a blank, omitting the propionaldehyde solution. Add 25.0 mL of a 2 g per L solution of ferric chloride to the test solution and to the blank, dilute with acetone to 100.0 mL, and mix. The absorbance of the test solution, measured at 660 nm using the blank as compensation liquid, is not less than 0.62.

(S)-()--Methylbenzyl Isocyanate C9H9NO—147.18[14649-03-7]—Use a suitable grade.

Methylene Blue, C16H18ClN3S·3H2O—373.90—Dark green crystals or a crystalline powder, having a bronze-like luster. One g dissolves in about 25 mL of water and in about 65 mL of alcohol. Soluble in chloroform. Use a suitable grade with a dye content of not less than 85%.

Methylene Chloride (Dichloromethane), CH2Cl2—84.93—Use ACS reagent grade Dichloromethane.

3-O-Methylestrone, C19H24O2—284.39—Use a suitable grade.
[NOTE—Commercially available as catalog number 1883-5 from Research Plus, Inc., P.O. Box 324, Bayonne, NJ 07002, fax number 908-754-2901, Web site: www.researchplus.com.]

2-Methyl-5-nitroimidazole, C4H4N3O2—127.10[88052-22-2]—Use a suitable grade.
[NOTE—Available as Catalog No. 13,625-5 from Sigma-Aldrich, www.sigma-aldrich.com.]

4-Methyl-2-pentanone (Methyl Isobutyl Ketone), (CH3)2CHCH2COCH3—100.16—Use ACS reagent grade.

2-Methyl-2-propyl-1,3-propanediol, C7H16O2—132.20—White crystals, melting at about 58.

N-Methylpyrrolidine (1-Methylpyrrolidine), C4H8NCH3—85.15[120-94-5]—Use ACS reagent grade.

Methyl Yellow (p-Dimethylaminoazobenzene), C14H15N3—225.3[60-11-7]—Use a suitable grade.

Mineral Acid —Use Hydrochloric Acid or Sulfuric Acid.

Molybdic Acid (85 Percent Molybdic Acid) —Use ACS reagent grade.

Monobasic Potassium Phosphate —See Potassium Phosphate, Monobasic.

Monobasic Sodium Phosphate —See Sodium Phosphate, Monobasic.

Monochloroacetic Acid, (Chloroacetic Acid, Chloroethanoic Acid) CH2ClCOOH—94.50—Use ACS reagent grade.

Monoethanolamine, (2-Aminoethanol) C2H7NO—61.08—Use ACS reagent grade.

Morpholine (Tetrahydro-1,4-oxazine), C4H9NO—87.12—Use ACS reagent grade.