Monograph pubs.acs.org/doi/book/10.1021/acsreagents
(1,2-Cyclohexylenedinitrilo)tetraacetic Acid (CDTA) 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 (1,2-Cyclohexylenedinitrilo)tetraacetic 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: Assay, Residue after Ignition, Heavy Metals, and Iron.
C14H22N2O8 · H2O (free acid monohydrate) C14H22N2O8 · H2O (free acid monohydrate) C14H20N2O8Na2 · 3H2O (disodium salt)
Formula Wt 364.35
CAS No. 125572-95-4
Formula Wt 364.35
CAS No. 145819-99-4
Formula Wt 444.35
CAS No. 57137-35-6
Note: This specification applies to both the free acid and disodium salt forms of this reagent. The residue after ignition test does not apply to the disodium salt form.
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . white solid
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4112 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Applications . . . . . . . . . . . . . . . . . . . . . . . . chelating agent Aqueous solubility . . . . . . . . . . . . . . . . . . . . slightly soluble
SPECIFICATIONS Assay (free acid) . . . . . . . . . . . . . . . . . . . . . 97.5–100.5% C14H22N2O8 · H2O Assay (disodium salt) . . . . . . . . . . . . . . . . . . ≥94.0% C14H20N2O8Na2 · 3H2O
Maximum Allowable Residue after ignition. . . . . . . . . . . . . . . . . . 0.2% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 0.001% Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.005%
TESTS Assay (By complexometry). For the free acid, weigh accurately about 0.75 g, and dissolve it in 50 mL of 0.1 N sodium hydroxide in a 250 mL beaker. For the disodium salt, weigh accurately about 0.95 g, and dissolve in 50 mL of water in a 250 mL beaker. Add 25 mL of water, 10 mL of ammonium acetate buffer solution, and 0.15 mL of phenolphthalein indicator solution. If necessary, neutralize the solution to the pink color of phenolphthalein by adding dropwise 10% ammonium hydroxide reagent solution. Add glacial acetic acid dropwise to a pH of 5.8 (using a pH meter). Add 0.10 mL of xylenol orange indicator solution. Titrate with 0.1 M zinc chloride volumetric solution to the change from yellow to magenta purple that remains for at least 1 min. One milliliter of 0.1 M zinc chloride corresponds to 0.03644 g of C14H22N2O8 · H2O and 0.04444 g of C14H20N2O8Na2 · 3H2O.
Residue after Ignition [Part 2: Gravimetric Methods; Residue after Ignition]. Use 3.0 g.
†
For the Determination of Heavy Metals and Iron
S a m p l e S o l u t i o n A . Ignite 3.0 g thoroughly, and heat in an oven at 600 °C until most of the carbon is volatilized. Cool, add 0.15 mL of nitric acid, and heat at 600 °C until all the carbon is volatilized. Dissolve the residue in 2 mL of dilute hydrochloric acid (1:1), digest in a covered dish on a hot plate (~100 °C) for 10 min, remove the cover, and evaporate to dryness. Dissolve in 1 mL of 1 N acetic acid and 20 mL of hot water, digest for 5 min, cool, and dilute with water to 30 mL (1 mL = 0.1 g).
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4112 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Heavy Metals
†
[Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dilute 20 mL of sample solution A (2 g sample) with water to 25 mL.
Iron† [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Use 2.0 mL of sample solution A (0.2 g sample).
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4112 ACS Reagent Chemicals, Part 4
