Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Lead Chromate 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 Lead Chromate 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, Soluble Matter, and Carbon Compounds.
PbCrO4
Formula Wt 323.20
CAS No. 7758-97-6
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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yellow or orange-yellow solid chemical analysis of organic substances melting point, 844 °C 0.2 mg per L of water
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥98.0% PbCrO4 Maximum Allowable Soluble matter . . . . . . . . . . . . . . . . . . . . . . 0.15% Carbon compounds (as C) . . . . . . . . . . . . . . . 0.01%
TESTS Assay (By titration of oxidizing power of chromate). Weigh accurately about 0.5 g of powdered sample, and dissolve by warming with 40 mL of 10% sodium hydroxide reagent solution in a glass-stoppered conical flask. Add 2 g of potassium iodide; when it is dissolved, dilute with 80 mL of water and 15 mL of hydrochloric acid. Stopper, swirl, and allow to stand in the dark for 5
© 2017 American Chemical Society
A
DOI:10.1021/acsreagents.4188 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
min. Titrate the liberated iodine with 0.1 N sodium thiosulfate volumetric solution, adding 3 mL of starch indicator solution near the end of the titration. One milliliter of 0.1 N sodium thiosulfate corresponds to 0.01077 g of PbCrO4.
Soluble Matter Boil 0.50 g of the powdered sample for 5 min with 100 mL of dilute acetic acid (1:20), stirring well during the heating. Cool, and filter. Evaporate 25 mL of the filtrate to dryness in a tared, preconditioned dish on a hot plate (~100 °C), and dry at 105 °C. Heat 50 mL of the filtrate with 2 g of the powdered sample for 5 min at 80–90 °C, cool, dilute with water to 50 mL, and filter. Evaporate 25 mL of this filtrate in a tared, preconditioned dish on a hot plate (~100 °C), and dry at 105 °C. The difference between the weights of the two residues should not be more than 0.0015 g.
Carbon Compounds This procedure uses induction heating of the sample and a conductometric measurement of evolved carbon dioxide. Transfer 1.0 g of sample and one tin capsule to a combustion crucible. Add 1.5 g each of iron and copper accelerator. Ignite in an induction furnace in a stream of carbon dioxide-free oxygen until combustion is complete. Pass the effluent gas through an approximately 0.1% solution of reagent-grade barium hydroxide. Measure the change in conductance, in mhos, using a suitable cell and detection system. Subtract the reading from a blank, and calculate the carbon content of the sample from a calibration curve. Prepare the calibration curve as follows: transfer 0, 10, 25, 75, and 100 µL of carbon standard solution (1 µL = 4 µg of carbon) to tin capsules. Evaporate the solutions to dryness in the capsules at 80 °C. Transfer the capsules to combustion crucibles, add the accelerators, ignite, and measure the conductance under the same conditions as described for running the sample. Subtract the reading of the blank from that of each of the standards, and plot the calibration curve as mhos versus micrograms of carbon.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4188 ACS Reagent Chemicals, Part 4
