Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Tannic Acid 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
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ABSTRACT This monograph for Tannic Acid 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: Identification, Loss on Drying, Residue after Ignition, Heavy Metals, Zinc, and Sugars, Dextrin.
CAS No. 1401-55-4
Note: For analytical purposes, tannic acid should be the hydrolyzable type, such as that isolated from nutgalls, sumac, or seed pods of Tara.
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . off-white to light brown solid Applications . . . . . . . . . . . . . . . . . . . . . . . . clarifying agent; pH control Aqueous solubility . . . . . . . . . . . . . . . . . . . . 1 g dissolves in 0.35 g
SPECIFICATIONS Identification . . . . . . . . . . . . . . . . . . . . . . . Passes test Maximum Allowable Loss on drying . . . . . . . . . . . . . . . . . . . . . . 12.0% Residue after ignition. . . . . . . . . . . . . . . . . . 0.5% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 0.003% Zinc (Zn) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.005% Sugars, dextrin . . . . . . . . . . . . . . . . . . . . . . Passes test
© 2017 American Chemical Society
A
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4391 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Identification To 2 mL of an aqueous 10% tannic acid solution, add 0.1 mL of an aqueous 5% lead nitrate solution. A precipitate forms immediately but completely dissolves on continued swirling to yield a clear solution.
Loss on Drying Weigh accurately 1.0 g, and dry at 105 °C to constant weight.
Residue after Ignition
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[Part 2: Gravimetric Methods; Residue after Ignition]. Ignite 5.0 g and moisten the char with 1 mL of sulfuric acid. Retain the residue for the test for zinc.
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Transfer 0.67 g into a 150 mL beaker, and cautiously add 15 mL of nitric acid and 5 mL of 70% perchloric acid. Evaporate the mixture to dryness on a hot plate (~100 °C) in a suitable hood, cool, add 2 mL of hydrochloric acid, and wash down the sides of the beaker with water. Carefully evaporate the solution to dryness on a hot plate (~100 °C), rotating the beaker to avoid spattering. Repeat the addition of 2 mL of hydrochloric acid, wash down the sides of the beaker with water, and again evaporate to dryness on a hot plate (~100 °C). Cool the residue, take up in 1 mL of hydrochloric acid and 10 mL of water, and dilute with water to 25 mL.
Zinc Dissolve the residue from the residue after ignition test in 2 mL of glacial acetic acid, dilute with 8 mL of water, and filter if necessary. Add 0.5 g of sodium acetate and 5 mL of freshly prepared hydrogen sulfide water, and mix. Any white turbidity should not exceed that produced by 0.25 mg of zinc ion (Zn) treated exactly as the sample residue.
Sugars, Dextrin Dissolve 2.0 g in 10 mL of water, and add 20 mL of ethyl alcohol. The mixture should be clear and should remain clear after standing for 1 h. Add 0.5 mL of ether. No turbidity should be produced.
© 2017 American Chemical Society
B
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4391 ACS Reagent Chemicals, Part 4
