Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Sodium Molybdate Dihydrate Part 4, Monographs for Reagent Chemicals: General Descriptions, Specifications, and Tests eISBN: 9780841230460 Tom Tyner Chair, ACS Committee on Analytical Reagents James Francis Secretary, ACS Committee on Analytical Reagents
ABSTRACT This monograph for Sodium Molybdate Dihydrate provides, in addition to common physical constants, a general description including typical appearance, applications, change in state (approximate), and aqueous solubility. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, pH of a 5% Solution at 25.0 °C, Insoluble Matter, Chloride, Phosphate, Sulfate, Ammonium, Heavy Metals, and Iron.
Na2MoO4 • 2H2O
Formula Wt 241.95
CAS No. 10102-40-6
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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white solid alkaloid reagent loses its water of crystallization at 100 °C 56 g in 100 mL at 0 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99.5–103.0% Na2MoO4 · 2H2O pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 7.0–10.5
Insoluble matter . . . Chloride (Cl) . . . . . Phosphate (PO4) . . . Sulfate (SO4) . . . . . Ammonium (NH4) . . Heavy metals (as Pb) Iron (Fe) . . . . . . . .
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© 2017 American Chemical Society
Maximum Allowable 0.005% 0.005% 5 ppm 0.015% 0.001% 5 ppm 0.001%
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DOI:10.1021/acsreagents.4355 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By oxidative titration after reduction of MoVI). Weigh accurately about 0.3 g, and dissolve in 10 mL of water in a 150 mL beaker. Activate the zinc amalgam of a Jones reductor by passing 100 mL of 1 N sulfuric acid through the column. Discard this acid, and place 25 mL of ferric ammonium sulfate solution (described below) in the receiver under the column. To the sample solution, add 100 mL of 1 N sulfuric acid, and pass this mixture through the reductor, followed by 100 mL of 1 N sulfuric acid and then 100 mL of water (using these to rinse the beaker). Add 5 mL of phosphoric acid to the solution in the receiver, and titrate with 0.1 N potassium permanganate volumetric solution. Run a blank, and make any necessary correction. One milliliter of 0.1 N potassium permanganate corresponds to 0.008066 g of Na2MoO4 · 2H2O.
For the Assay
F e r r i c A m m o n i u m S u l f a t e S o l u t i o n . Dissolve 50 g of ferric ammonium sulfate dodecahydrate in 500 mL of solution containing 25 mL of sulfuric acid.
pH of a 5% Solution at 25.0 °C [Part 2: Direct Electrometric Methods; pH Potentiometry; pH Range; Procedure for pH of a 5% Solution at 25.0 °C].
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 20 g dissolved in 200 mL of water.
Chloride Dissolve 1.0 g in 50 mL of water, and mix. Pipette 10 mL of the solution into a color-comparison tube, add 2 mL of nitric acid, dilute with water to 25 mL, and add 1 mL of silver nitrate reagent solution. Any turbidity should not exceed that produced by 0.01 mg of chloride ion (Cl) in an equal volume of solution containing the quantities of reagents used in the test.
Phosphate [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 3 (Precipitation)].
Sulfate [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 2]. Dissolve in a mixture of 5 mL of water and 5 mL of nitric acid. Evaporate to dryness on a hot plate. Digest the residue with a mixture of 1 mL of hydrochloric acid and 10 mL of water. Dilute to 20 mL, and filter through two prewashed fine-porosity papers. Add 12% barium chloride reagent solution to the clear filtrate, and use Method 1.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4355 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Ammonium Dissolve 1.0 g in 20 mL of water, add 10 mL of 10% sodium hydroxide reagent solution, and dilute with water to 50 mL. For the standard, add 0.01 mg of ammonium ion (NH4) to 20 mL of water, add 10 mL of 10% sodium hydroxide reagent solution, and dilute with water to 50 mL. To each solution, add 2 mL of Nessler reagent. Any color produced in the sample solution should not exceed that in the standard.
Heavy Metals Dissolve 6.0 g in 35 mL of 10% sodium hydroxide reagent solution, add 5 mL of ammonium hydroxide, and dilute with water to 42 mL. For the control, add 0.02 mg of lead to 7.0 mL of the solution, and dilute with water to 40 mL. For the sample, dilute the remaining 35 mL portion with water to 40 mL. Add 10 mL of freshly prepared hydrogen sulfide water to each, and mix. Any color in the solution of the sample should not exceed that in the control.
Iron (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).
For the Determination of Iron
S a m p l e S t o c k S o l u t i o n . Dissolve 10.0 g in water, and dilute with water to 100 mL (1 mL = 0.10 g).
For the Determination of Iron
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Fe
248.3
2.50
0.05; 0.10
A/A
Yes
*A/A is air/acetylene.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4355 ACS Reagent Chemicals, Part 4
