Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Dithizone ((Phenylazo)thioformic Acid 2-Phenylhydrazide; Diphenylthiocarbazone) 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 Dithizone 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, Ratio of Absorbances, Residue after Ignition, and Heavy Metals.
C6H5NHNHCSN:NC6H5
Formula Wt 256.33
CAS No. 60-10-6
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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black or purple-black crystalline solid indicator for determination of cadmium, lead, and mercury melting point, 168 °C; decomposes insoluble
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥85.0% C6H5NHNHCSN:NC6H5 Ratio of absorbances . . . . . . . . . . . . . . . . . . ≥1.55 Maximum Allowable Residue after ignition. . . . . . . . . . . . . . . . . . 0.3% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 0.002%
© 2017 American Chemical Society
A
DOI:10.1021/acsreagents.4130 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By spectrophotometry). Weigh accurately 10.0 mg, transfer to a 100 mL volumetric flask, dissolve in about 75 mL of chloroform, and dilute to volume with chloroform. Dilute 5.0 mL of this solution to 100.0 mL with chloroform, and determine the absorbance of this solution in 1.00 cm cells at 620 nm, using chloroform as the blank. Reserve the remainder of the solution for determining the ratio of absorbances. Determine the molar absorptivity by dividing the absorbance by 1.95 × 10–5 (the molar concentration of the dithizone), and calculate the assay value as follows:
Ratio of Absorbances Determine the molar absorptivity at 450 nm of the solution prepared in the test for assay, using the method described in the test. The ratio of the value at 620 nm to that at 450 nm should not be less than 1.55.
Residue after Ignition [Part 2: Gravimetric Methods; Residue after Ignition]. Ignite 1.0 g. Moisten the char with 1 mL of nitric acid and 1 mL of sulfuric acid.
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 2]. Use 1.0 g.
© 2017 American Chemical Society
B
DOI:10.1021/acsreagents.4130 ACS Reagent Chemicals, Part 4
