Potassium Thiocyanate - American Chemical Society

Monograph pubs.acs.org/doi/book/10.1021/acsreagents

Potassium 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

Downloaded by CORNELL UNIV on May 30, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4309

ABSTRACT This monograph for Potassium 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 in Water, Chloride, Sulfate, Ammonium, Heavy Metals, Iron, Sodium, Iodine-Consuming Substances. Special caution is advised for the handling or testing of this substance.

KSCN

Formula Wt 97.18

CAS No. 333-20-0

GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . colorless or white solid Applications . . . . . . . . . . . . . . . . . . . . . . . . analysis of silver ion; indirect determination of chloride, bromide, and iodide Change in state (approximate) . . . . . . . . . . . . melting point, 173°C Aqueous solubility . . . . . . . . . . . . . . . . . . . . 217 g in 100 mL at 20 °C

SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥98.5% KSCN pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 5.3–8.7 Maximum Allowable Insoluble in water . . . . . . . . . . . . . . . . . . . . 0.005% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Ammonium (NH4) . . . . . . . . . . . . . . . . . . . . 0.003% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 5 ppm Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 2 ppm Sodium (Na) . . . . . . . . . . . . . . . . . . . . . . . . 0.005% Iodine-consuming substances . . . . . . . . . . . . . Passes test

© 2017 American Chemical Society

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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.

DOI:10.1021/acsreagents.4309 ACS Reagent Chemicals, Part 4

ACS Reagent Chemicals

Monograph

pubs.acs.org/doi/book/10.1021/acsreagents

TESTS C a u t i o n : Cyanide gases are given off during ignition and with addition of acids. Use a well-ventilated hood.


Assay (By argentimetric titration of thiocyanate content). Weigh, to the nearest 0.1 mg, about 7 g of sample, dissolve with 100 mL of water in a 1 L volumetric flask, dilute to the mark with water, and mix thoroughly. Transfer a 50.0 mL aliquot to a 250 mL glass-stoppered iodine-type flask, add 5 mL of 1 N nitric acid, then add with agitation exactly 50.0 mL of 0.1 N silver nitrate volumetric solution, and shake vigorously. Add 2 mL of ferric ammonium sulfate indicator solution, and chill in an ice bath to approximately 10 °C or lower. Titrate the excess silver nitrate with 0.1 N ammonium thiocyanate volumetric solution. Near the end point, shake after the addition of each drop. One milliliter of 0.1 N silver nitrate corresponds to 0.009718 g of KSCN.

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 in Water Dissolve 20 g in 200 mL of water, heat to boiling, and digest in a covered beaker on a hot plate (~100 °C) for 1 h. Filter through a tared, preconditioned filtering crucible, wash thoroughly, and dry at 105 °C.

Chloride Dissolve 1.0 g in 20 mL of water, filter if necessary through a chloride-free filter, and 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 15–20 mL of water, and evaporate again. Repeat until all the cyanide has been volatilized, cool, and dilute with water to 100 mL. To 20 mL of this solution, add 1 mL of nitric acid and 1 mL of silver nitrate reagent solution. Any turbidity should not exceed that produced by 0.01 mg of chloride ion (Cl) in an equal volume of solution containing the quantities of reagents used in the test.

Sulfate [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 1]. Allow 30 min for turbidity to form.

Ammonium (By colorimetry, [Part 2: Colorimetry and Turbidimetry; Ammonium (Test for Ammonia and Amines)]). Dilute the distillate from a 1.0 g sample to 100 mL; 50 mL of the dilution should not show more than 0.015 mg of ammonium ion (NH4).


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ACS Reagent Chemicals

Monograph

pubs.acs.org/doi/book/10.1021/acsreagents

Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dissolve 6.0 g in about 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 2 (Hydroxylamine and 1,10-Phenanthroline)]. Dissolve 10 g in 60 mL of water. To 30 mL of the solution, add 0.1 mL of hydrochloric acid, and continue as described.

Sodium


(By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).

For the Determination of Sodium

S a m p l e S t o c k S o l u t i o n . Dissolve 1.0 g of sample with water in a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.01 g).

For the Determination of Sodium

Element

Wavelength (nm)

Sample Wt (g)

Standard Added (mg)

Flame Type*

Background Correction

Na

589.0

0.10

0.005; 0.01

A/A

No

*A/A is air/acetylene.

Iodine-Consuming Substances Dissolve 5.0 g in 50 mL of water and add 1.7 mL of 10% sulfuric acid reagent solution. Add 1 g of potassium iodide and 1 mL of starch indicator solution, and titrate with 0.1 N iodine volumetric solution. Not more than 1.0 mL of 0.1 N iodine solution should be required.


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Potassium Thiocyanate - American Chemical Society

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