Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Ammonium Thiocyanate 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 Ammonium Thiocyanate 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, pH of a 5% Solution at 25.0 °C, Insoluble Matter, Residue after Ignition, Chloride, Sulfate, Heavy Metals, Iron, and Iodine-Consuming Substances.
NH4SCN
Formula Wt 76.12
CAS No. 1762-95-4
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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colorless, deliquescent solid determination of iron, mercury, and silver melting point, 149 °C 165 g in 100 mL at 20 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥97.5% NH4SCN pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 4.5–6.0 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.005% Residue after ignition. . . . . . . . . . . . . . . . . . 0.025% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 5 ppm Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 3 ppm Iodine-consuming substances . . . . . . . . . . . . . 0.004 meq/g
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4037 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By argentimetric titration of thiocyanate content). Weigh, to the nearest 0.1 mg, 7 g of sample. Dissolve with 100 mL of water in a 1 L volumetric flask, dilute with water to the mark, and mix well. Transfer a 50.0 mL aliquot to a 250 mL glassstoppered iodine-type flask, add 15 mL of 10% nitric acid reagent solution, then add with agitation exactly 50.0 mL of 0.1 N silver nitrate volumetric solution, and stir vigorously. Add 2 mL of ferric ammonium sulfate indicator solution, and titrate the excess silver nitrate with 0.1 N ammonium thiocyanate volumetric solution. Near the end point, stir after the addition of each drop. One milliliter of 0.1 N silver nitrate corresponds to 0.007612 g of NH4SCN.
pH of a 5% Solution at 25.0 °C [Part 2: Direct Electrometric Methods; pH Potentiometry; pH Range; Procedure for pH of a 5% Solution at 25.0 °C].
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 20 g dissolved in 150 mL of water.
Residue after Ignition [Part 2: Gravimetric Methods; Residue after Ignition]. Ignite 3.3 g. Retain the residue for the test for iron.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Dissolve 1.0 g in 20 mL of water in a small flask. Add 10 mL of 25% sulfuric acid reagent solution and 7 mL of 30% hydrogen peroxide. Evaporate to 20 mL by boiling in a well-ventilated hood, add 17 mL of water, and evaporate again. Repeat until all the cyanide has been volatilized. Cool, filter if necessary through a chloride-free filter, and dilute with water to 100 mL. Use 20 mL of this solution.
Sulfate [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 1]. Use 1.0 g sample, and allow 30 min for turbidity to form.
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dissolve 6.0 g in 20 mL of water, and dilute with water to 30 mL. Use 25 mL to prepare the sample solution, and use the remaining 5.0 mL to prepare the control solution.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. To the residue after ignition 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 2 mL of hydrochloric acid, filter if necessary, and dilute with water to 50 mL. Use the solution without further acidification.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4037 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Iodine-Consuming Substances Dissolve 5.0 g in 50 mL of water plus 1.7 mL of 10% sulfuric acid reagent solution. Add 1 g of potassium iodide and 2 mL of starch indicator solution, and titrate with 0.01 N iodine solution. Not more than 2.0 mL of the iodine solution should be required.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4037 ACS Reagent Chemicals, Part 4
