Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Ammonium Sulfide Solution 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 Ammonium Sulfide Solution 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, Carbonate, and Chloride.
(NH4)2S
Formula Wt 68.14
CAS No. 12135-76-1
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . yellow liquid Applications . . . . . . . . . . . . . . . . . . . . . . . . reagent for trace heavy metal analysis Aqueous solubility . . . . . . . . . . . . . . . . . . . . soluble
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.0–24.0% (NH4)2S Maximum Allowable Residue after ignition. . . . . . . . . . . . . . . . . . 0.04% Carbonate (CO2) . . . . . . . . . . . . . . . . . . . . . 0.005% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.005%
TESTS Assay (By titration of reductive capacity). Weigh accurately about 3.0 g, and in a 250 mL volumetric flask, dilute with water through which nitrogen has been freshly bubbled to expel oxygen. Dilute to volume with similar water, and displace air from the headspace with nitrogen. Stopper, and mix thoroughly. Place a 50.0 mL aliquot of this solution into a mixture of 50.0 mL of 0.1 N iodine and 25 mL of 0.1 N hydrochloric acid in 400 mL of water. Be sure that the tip of the pipette is below the
© 2017 American Chemical Society
A
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4036 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
surface of the iodine when adding the ammonium sulfide. Titrate the excess of iodine with 0.1 N sodium thiosulfate volumetric solution, adding 3 mL of starch indicator solution near the end point of the titration. One milliliter of 0.1 N iodine corresponds to 0.00341 g of (NH4)2S.
Residue after Ignition [Part 2: Gravimetric Methods; Residue after Ignition]. Evaporate 5.0 mL (5.0 g) to dryness, and proceed as directed.
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Carbonate Dilute 4.0 mL (4.0 g) of sample to 20 mL in a suitable Nessler tube. For the standard, dilute 1.0 mL of the carbonate (0.2 mg/mL of CO2) standard solution to 20 mL in a matched Nessler tube. Add 3 mL of 12% barium chloride reagent solution, and gently heat both solutions for 1 min in a boiling water bath. The turbidity in the sample should not exceed that in the standard.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Dilute 0.5 mL (0.5 g ) to 20 mL with water, add 2 mL of hydrogen peroxide, and evaporate to dryness. Dissolve the residue in water to make 50 mL. Use 20 mL for the sample solution.
© 2017 American Chemical Society
B
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4036 ACS Reagent Chemicals, Part 4
