Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Sodium Sulfide, Nonahydrate 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 Sodium Sulfide, Nonahydrate 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, Ammonium, Sulfite, Thiosulfate, and Iron.
Na2S • 9H2O
Formula Wt 240.18
CAS No. 1313-84-4
Note: To enhance stability, storage below 10 °C is recommended.
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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colorless or slightly yellow solid source of hydrogen sulfide for heavy metals tests melting point, 50 °C 47 g in 100 mL at 10 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥98.0% Na2S · 9H2O Maximum Allowable Ammonium (NH4) . . . . . . . . . . . . . . . . . . . . 0.005% Sulfite and thiosulfate (as SO4) . . . . . . . . . . . . 0.1% Iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Passes test
© 2017 American Chemical Society
A
DOI:10.1021/acsreagents.4370 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By titration of reductive capacity). Weigh accurately about 2.5 g, and in a 250 mL volumetric flask, dilute with water through which high-purity nitrogen gas has been freshly bubbled to expel oxygen. Dilute to volume with similar water, and displace air from the headspace with nitrogen gas. 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 volumetric solution and 25 mL of 0.1 N hydrochloric acid in 400 mL of water. Titrate the excess 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 iodine consumed corresponds to 0.01201 g of Na2S · 9H2O.
Ammonium (By colorimetry, [Part 2: Colorimetry and Turbidimetry; Ammonium (Test for Ammonia and Amines)]). Dissolve 1.0 g in 80 mL of water, add 20 mL of lead acetate reagent solution, and allow to stand until the precipitate has settled. Decant 50 mL of the clear supernatant liquid, and use the 50 mL for distillation. For the standard, use 0.025 mg of ammonium ion (NH4) treated exactly as the sample.
Sulfite and Thiosulfate (Note: The water used in this test must be free from dissolved oxygen.) Dissolve 3.0 g in 200 mL of water and add 100 mL of 5% zinc sulfate solution. Mix thoroughly; allow to stand for 30 min. Filter, and titrate 100 mL of the filtrate with 0.01 N iodine, using starch indicator solution. Not more than 4.0 mL of the iodine solution should be required.
Iron Dissolve 5.0 g in 100 mL of water. The solution should be clear and colorless.
© 2017 American Chemical Society
B
DOI:10.1021/acsreagents.4370 ACS Reagent Chemicals, Part 4
