Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Potassium Cyanide 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 Potassium Cyanide 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, Chloride, Phosphate, Sulfate, Sulfide, Thiocyanate, Iron, Total, Lead, and Sodium.
KCN
Formula Wt 65.12
CAS No. 151-50-8
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
white solid complexing agent in alkaline solutions melting point, 634 °C 72 g in 100 mL at 25 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥96.0% KCN
Chloride (Cl) . . . . Phosphate (PO4) . . Sulfate (SO4) . . . . Sulfide (S) . . . . . . Thiocyanate (SCN) . Iron, total (as Fe) . Lead (Pb) . . . . . . Sodium (Na) . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
© 2017 American Chemical Society
Maximum Allowable 0.5% 0.005% 0.04% 0.003% Passes test 0.03% 2 ppm 0.5%
A
DOI:10.1021/acsreagents.4285 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By argentimetric titration of cyanide content). Weigh accurately about 0.5 g, and dissolve in 30 mL of water. Add 0.2 mL of 10% potassium iodide reagent solution and 1 mL of ammonium hydroxide, and titrate with 0.1 N silver nitrate volumetric solution to a slight yellowish permanent turbidity. One milliliter of 0.1 N silver nitrate corresponds to 0.01302 g of KCN.
†
For the Determination of Chloride, Phosphate, Sulfate, Sulfide, Thiocyanate, and Total Iron
S a m p l e S o l u t i o n A . Dissolve 10 g in water, and dilute with water to 200 mL. Filter, if necessary, under a wellventilated fume hood into a dry flask (1 mL = 0.05 g).
Chloride† [Part 2: Colorimetry and Turbidimetry; Chloride]. Dilute 1.0 mL of sample solution A with water to 50 mL. To 2.0 mL (0.002 g sample) of this solution, add 2 mL of 30% hydrogen peroxide, and allow to stand in a covered beaker until reaction ceases, then digest in the covered beaker on a hot plate (~100 °C) for 20–30 min. Cool, and dilute with water to 25 mL.
Phosphate† [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 1 (Direct Molybdenum Blue)]. To 20 mL of sample solution A, add 2 mL of hydrochloric acid, and evaporate to dryness in a well-ventilated hood. Add 5 mL of dilute hydrochloric acid (1:1), and evaporate to dryness again. Dissolve in 50 mL of approximately 0.5 N sulfuric acid. To 20 mL of the solution, add 5 mL of approximately 0.5 N sulfuric acid, and continue as described.
Sulfate† [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 2]. Use 2.5 mL of sample solution A plus 1 mL of dilute hydrochloric acid (1:1) in a hood.
Sulfide† To 20 mL of sample solution A (measured in a graduated cylinder) (1 g sample), add 0.15 mL of alkaline lead solution (made by adding 10% sodium hydroxide reagent solution to a 10% lead acetate reagent solution until the precipitate is redissolved). The color should not be darker than is produced by 0.03 mg of sulfide ion (S) in an equal volume of solution when treated with 0.15 mL of the alkaline lead solution.
Thiocyanate† To 20 mL of sample solution A (measured in a graduated cylinder) (1 g sample), add 4 mL of hydrochloric acid and 0.20 mL of 5% ferric chloride reagent solution. At the end of 5 min, the solution should show no reddish tint when compared with 20 mL of water to which have been added the quantities of hydrochloric acid and ferric chloride used in the test. (Limit about 0.02%.)
© 2017 American Chemical Society
B
DOI:10.1021/acsreagents.4285 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
†
Iron, Total
[Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Transfer 10 mL of sample solution A (0.5 g sample) to a platinum evaporating dish, add 3 mL of hydrochloric acid, and evaporate to dryness in a well-ventilated hood. Heat the residue at 650 °C for 30 min. Cool, add 2 mL of hydrochloric acid and 10 mL of water, and digest on a hot plate (~100 °C) until dissolution is complete. Dilute with water to 30 mL, and use 2.0 mL of this solution.
Lead Dissolve 1.2 g in 10 mL of water in a separatory funnel. Add 5 mL of ammonium citrate reagent solution, 2 mL of hydroxylamine hydrochloride reagent solution for the dithizone test, and 0.10 mL of phenol red indicator solution, and make the solution alkaline if necessary by the addition of ammonium hydroxide. Add 5 mL of dithizone test solution, shake gently but well for 1 min, and allow the layers to separate. The intensity of the red color of the chloroform layer should be no greater than that of a control made with 0.002 mg of lead ion (Pb) and 0.2 g of the sample treated exactly like the solution of 1.2 g of sample in 10 mL of water.
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 0.5 g of sample in a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.005 g).
For the Determination of Sodium
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Na
589.0
0.01
0.05; 0.10
A/A
No
*A/A is air/acetylene.
© 2017 American Chemical Society
C
DOI:10.1021/acsreagents.4285 ACS Reagent Chemicals, Part 4
