Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Phthalic Acid (1,2-Benzenedicarboxylic 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
ABSTRACT This monograph for Phthalic Acid provides, in addition to common physical constants, a general description including typical appearance, applications, aqueous solubility, and pKa. 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, Nitrate, Sulfate, Heavy Metals, Iron, and Water.
C6H4(COOH)2
Formula Wt 166.13
CAS No. 88-99-3
GENERAL DESCRIPTION Typical appearance Applications . . . . . Aqueous solubility . pKa . . . . . . . . . .
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white solid buffers 0.6 g in 100 mL at 20 °C 3.0
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.5% C6H4(COOH)2 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.05% Residue after ignition (as SO4) . . . . . . . . . . . . 0.02% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Nitrate (NO3) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 0.001% Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.001% Water (H2O) . . . . . . . . . . . . . . . . . . . . . . . . 0.5%
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4271 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By acid–base titrimetry). Weigh accurately about 2.8 g, transfer to a conical flask, cool, and add 50.0 mL of 1 N sodium hydroxide volumetric solution. Add 25 mL of water, and boil on a hot plate until dissolved. Add 0.15 mL of phenolphthalein indicator solution, and titrate the excess sodium hydroxide with 1 N hydrochloric acid volumetric solution. Perform a blank determination, and make any necessary correction. One milliliter of 1 N sodium hydroxide consumed corresponds to 0.08306 g of C6H4(COOH)2.
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 10.0 g dissolved in 250 mL of 10% sodium carbonate solution.
Residue after Ignition [Part 2: Gravimetric Methods; Residue after Ignition]. Use 4.0 g. Retain the residue to prepare sample solution B for the tests for heavy metals and iron.
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For the Determination of Chloride, Nitrate, and Sulfate
S a m p l e S o l u t i o n A . Dissolve 10.0 g in 100 mL of boiling water, and allow to cool to room temperature. The supernatant liquid after decantation from the crystallized phthalic acid is sample solution A (1 mL = 0.10 g).
Chloride† [Part 2: Colorimetry and Turbidimetry; Chloride]. Dilute 10 mL of sample solution A (1.0 g sample) to 20 mL with water. Filter if necessary through a chloride-free filter. For the standard, use 0.01 mg of chloride ion (Cl) and dilute to 20 mL with water. To each, add 1 mL of nitric acid and 1 mL of silver nitrate reagent solution. Mix, allow to stand for 5 min protected from sunlight, and compare. The solutions can best be viewed visually against a black background. Any turbidity in the solution of the sample should not exceed that in the standard.
Nitrate† [Part 2: Colorimetry and Turbidimetry; Nitrate; Procedure for Nitrate, Method 1 (Brucine Sulfate)]. Use 10 mL of sample solution A (1 g sample) and 0.05 mg of nitrate ion (NO3).
Sulfate† [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 3]. Add 1 mL of 1% sodium carbonate reagent solution to 10 mL of sample solution A (1 g sample), and evaporate to dryness on a hot plate (~100 °C). Redissolve in a minimum volume of water, and add 1 mL of dilute hydrochloric acid (1:19). If necessary, filter through a small filter, and wash with two 2 mL portions of water. Dilute to 10 mL, and add 1 mL of 12% barium chloride reagent solution. Any turbidity should not exceed that produced by 0.05 mg of sulfate ion (SO4) in an equal volume of solution containing the quantities of reagents used in the test. Compare 30 min after adding the barium chloride to the sample and standard solutions.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4271 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
‡
For the Determination of Heavy Metals and Iron
S a m p l e S o l u t i o n B . To the residue after ignition, add 10 mL of water, and dilute to 20 mL (1 mL = 0.2 g).
Heavy Metals‡ [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Use 10 mL of sample solution B (2.0 g sample).
Iron‡ [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 2 (Hydroxylamine and 1,10-Phenanthroline)]. Use 5 mL of sample solution B (1.0 g sample).
Water [Part 2: Titrimetric Methods; Water by the Karl Fischer Method; Volumetric Procedure; Volumetric Procedure for Samples Using Karl Fischer Reagent, Method 1]. Use 5.0 g.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4271 ACS Reagent Chemicals, Part 4
