Ammonium Molybdate USP

(NH4)6Mo7O24-4H2O 1235.86
Molybdate (Mo7O24 6 ), hexaammonium, tetrahydrate.
Hexaammonium molybdate tetrahydrate [12054-85-2].

Ammonium Molybdate contains not less than 99.3 percent and not more than 101.8 percent of (NH4)6Mo7O244H2O.

Identification: Dissolve 0.6 g of it in 1.4 mL of water and 1.45 mL of ammonium hydroxide. Cool this mixture, and add slowly, with mixing, 7.2 mL of a well-cooled mixture of 3.2 mL of nitric acid and 4 mL of water. Allow to stand for 24 to 48 hours, and filter through a sintered-glass filter. To 5 mL of the filtrate add 2 mL of dibasic sodium phosphate TS: a yellow precipitate is formed, and it is soluble in an excess of 6 N ammonium hydroxide.
Insoluble substances:Dissolve 20 g in 200 mL of water in a beaker, heat to boiling, cover, and heat on a steam bath for 1 hour. Filter the hot solution through a tared filtering crucible, wash the insoluble residue with hot water, and dry at 105 for 2 hours: the weight of the residue so obtained does not exceed 1 mg (0.005%).
Chloride: Maximum 0.002%.
Limit of nitrate: To pass the test.
Sulfate: Maximum 0.02%.
Arsenate, phosphate, and silicate: To pass the test.
Phosphate: Maximum 5 ppm.
Magnesium and alkali salts: Maximum 0.02%.
Heavy metals: The limit is 10 µg per g.
Assay: Dissolve about 1 g of Ammonium Molybdate, accurately weighed, in a mixture of 10 mL of water and 1 mL of ammonium hydroxide in a 250-mL volumetric flask, dilute with water to volume, and mix. Filter the solution, and transfer 50.0 mL of the filtrate to a 600-mL beaker. Add 250 mL of water, 20 g of ammonium chloride, 15 mL of hydrochloric acid, and 0.15 mL of methyl orange TS, heat nearly to boiling, and add 18 mL of lead acetate TS. To the hot solution add, slowly and with constant stirring, a saturated solution of ammonium acetate until the color turns yellow, and then add 15 mL of lead acetate TS. Cover the beaker, and heat just below the boiling temperature until the precipitate has settled. Filter through a tared, porous porcelain crucible, wash with seven or eight successive portions of a mixture of water, saturated ammonium acetate solution, and nitric acid (890:100:10), and finally wash with three successive portions of hot water. Ignite to constant weight at 560C to 625C. Each mg of the lead molybdate so obtained is equivalent to 0.4809 mg of (NH4)6Mo7O244H2O.

Ammonium Molybdate Tetrahydrate ACS AR Analytical Reagent grade

(NH4)6Mo7O24 · 4H2O
Formula Wt 1235.86
CAS Number 12027-67-7

REQUIREMENTS

MAXIMUM ALLOWABLE

Insoluble matter	0.005%
Chloride (Cl)	0.002%
Nitrate (NO3)	Passes test
Arsenate, phosphate, and silicate (as SiO2)	0.001%
Phosphate (PO4)	5 ppm
Sulfate (SO4)	0.02%
Heavy metals (as Pb)	0.001%
Magnesium (Mg)	0.005%
Potassium (K)	0.002%
Sodium (Na)	0.01%