Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Ammonium Citrate, Dibasic (Citric Acid, Diammonium Salt; 2-Hydroxy-1,2,3-propanetricarboxylic Acid, Diammonium Salt) 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 Ammonium Citrate, Dibasic provides, in addition to common physical constants, a general description including typical appearance, applications, 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, Insoluble Matter, Residue after Ignition, Chloride, Heavy Metals, Iron, Oxalate, Phosphate, and Sulfur Compounds.
(NH4)2HC6H5O7
Formula Wt 226.19
CAS No. 3012-65-5
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . colorless solid Applications . . . . . . . . . . . . . . . . . . . . . . . . determination of phosphates Aqueous solubility . . . . . . . . . . . . . . . . . . . . very soluble
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98.0–103.0% (NH4)2HC6H5O7
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4021 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Insoluble matter . . . . . . . Residue after ignition. . . . Chloride (Cl) . . . . . . . . . Heavy metals (as Pb) . . . . Iron (Fe) . . . . . . . . . . . . Oxalate (C2O4) . . . . . . . . Phosphate (PO4) . . . . . . . Sulfur compounds (as SO4).
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Maximum Allowable 0.005% 0.01% 0.001% 5 ppm 0.001% Passes test 5 ppm 0.005%
TESTS Assay (By alkalimetry for ammonium). Weigh accurately about 3.0 g of sample and dissolve in 50 mL of water in a 500 mL Erlenmeyer flask. Add exactly 50.0 mL of 1 N sodium hydroxide volumetric solution, place a filter funnel loosely in the neck of the flask, and boil until all the ammonia is expelled (about 10–15 min) as determined with litmus paper. Cool, and add 0.15 mL of thymol blue indicator solution. Titrate the excess sodium hydroxide with 1 N sulfuric acid. One milliliter of 1 N sodium hydroxide corresponds to 0.07540 g of (NH4)2HC6H5O7.
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 20 g dissolved in 200 mL of water.
Residue after Ignition [Part 2: Gravimetric Methods; Residue after Ignition]. Ignite 10 g.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 1.0 g.
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dissolve 6.0 g in about 20 mL of water, add 5 mL of dilute hydrochloric acid (1:1), and dilute with water to 30 mL. Use 25 mL to prepare the sample solution, and use the remaining 5.0 mL to prepare the control solution.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Use 1.0 g.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4021 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Oxalate Dissolve 5.0 g in 25 mL of water, and add 3 mL of glacial acetic acid and 2 mL of 10% calcium acetate solution. No turbidity or precipitate should appear after standing 4 h. (Limit about 0.05%.)
Phosphate [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 1 (Direct Molybdenum Blue)]. Mix 4.0 g with 0.5 g of magnesium nitrate hexahydrate in a platinum dish and ignite. Dissolve the residue in 5 mL of water, add 5 mL of nitric acid, and evaporate to dryness. Dissolve the residue in 25 mL of approximately 0.5 N sulfuric acid, and continue as described.
Sulfur Compounds To 1.0 g, add 1 mL of hydrochloric acid and 3 mL of nitric acid. Prepare a standard containing 0.05 mg of sulfate ion (SO4), 1 mL of hydrochloric acid, and 3 mL of nitric acid. Digest each in a covered beaker on a hot plate (~100 °C) until the reaction ceases, remove the covers, and evaporate to dryness. Add 0.2–0.5 mg of ammonium vanadate and 10 mL of nitric acid, and digest in covered beakers on the hot plate until reactions cease. Remove the covers, and evaporate to dryness. Add 10 mL more of nitric acid, and repeat the digestions and evaporations. Add 5 mL of dilute hydrochloric acid (1:1), and evaporate to dryness. Dissolve the residues in 4 mL of water plus 1 mL of dilute hydrochloric acid (1:19), and filter through a small filter. Wash with two 2 mL portions of water, dilute with water to 10 mL, and add 1 mL of 12% barium chloride reagent solution to each. Any turbidity in the solution of the sample should not exceed that in the standard. Compare 10 min after adding the barium chloride to the sample and standard solutions.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4021 ACS Reagent Chemicals, Part 4
