Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Silver Sulfate 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 Silver Sulfate 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, Insoluble Matter, Silver Chloride, Nitrate, Substances Not Precipitated by Hydrochloric Acid, and Iron.
Ag2SO4
Formula Wt 311.79
CAS No. 10294-26-5
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
colorless or white solid; may darken on exposure to light titrimetric reagent melting point, 657 °C 0.8 g in 100 mL at 20 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥98.0% Ag2SO4 Maximum Allowable Insoluble matter and silver chloride. . . . . . . . . 0.02% Nitrate (NO3) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Substances not precipitated by hydrochloric acid 0.03% Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.001%
© 2017 American Chemical Society
A
DOI:10.1021/acsreagents.4323 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By argentimetric titrimetry). Weigh, to the nearest 0.1 mg, about 0.5 g of sample in a 250 mL Erlenmeyer flask. Dissolve in 50 mL of water and 5 mL of nitric acid. Add 2 mL of ferric ammonium sulfate indicator solution, and titrate with 0.1 N potassium thiocyanate to the first appearance of a reddish-brown end point. One milliliter of 0.1 N potassium thiocyanate corresponds to 0.01559 g of Ag2SO4.
Insoluble Matter and Silver Chloride Add 5.0 g of the powdered salt to 500 mL of boiling water, and boil gently until the silver sulfate is dissolved. If any insoluble matter remains, filter while hot through a tared, preconditioned filtering crucible (retain the filtrate for the test for substances not precipitated by hydrochloric acid), wash thoroughly with hot water (discard the washings), and dry at 105 °C.
Nitrate To 0.50 g of the powdered salt, add 2 mL of phenoldisulfonic acid reagent solution, and heat on a hot plate (~100 °C) for 15 min. Cool, dilute with 20 mL of water, filter, and make alkaline with ammonium hydroxide. Any yellow color should not exceed that produced when a solution containing 0.005 mg of nitrate ion (NO3) is evaporated to dryness and the residue is treated in the same manner as the sample.
Substances Not Precipitated by Hydrochloric Acid Heat to boiling the filtrate obtained in the test for insoluble matter and silver chloride, add 5 mL of hydrochloric acid, and allow to stand for at least 8 h. Dilute with water to 500 mL, and filter. Evaporate 250 mL of the filtrate to dryness, and add 0.15 mL of hydrochloric acid and 10 mL of water. Heat and filter. Add 0.10 mL of sulfuric acid to the resulting filtrate, evaporate to dryness in a tared, preconditioned dish, and ignite at 600 ± 25 °C for 15 min. Correct for the weight obtained in a complete blank test. Retain the residue for the test for iron.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. To the residue obtained in the test for substances not precipitated by hydrochloric acid, add 3 mL of dilute hydrochloric acid (1:1), cover with a watch glass, and digest on a hot plate (~100 °C) for 15–20 min. Remove the watch glass, and evaporate to dryness. Dissolve the residue in 35 mL of dilute hydrochloric acid (1:6), filter if necessary, and dilute with water to 50 mL. Use 20 mL of the solution without further acidification.
© 2017 American Chemical Society
B
DOI:10.1021/acsreagents.4323 ACS Reagent Chemicals, Part 4
