Potassium Chloride - ACS Reagent Chemicals (ACS Publications)

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

Potassium Chloride 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 1, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4283

ABSTRACT This monograph for Potassium Chloride 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, Iodide, Bromide, Chlorate, Nitrate, Phosphate, Sulfate, Barium, Heavy Metals, Iron, Calcium, Magnesium, and Sodium.

KCl

Formula Wt 74.55

CAS No. 7447-40-7

GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .

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colorless or white solid buffer solutions melting point, 773 °C 35 g in 100 mL at 20 °C

SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99.0–100.5% KCl pH of a 5% solution at 25.0 °C . . . . . . . . . 5.4–8.6 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.005% Iodide (I). . . . . . . . . . . . . . . . . . . . . . . . . . 0.002% Bromide (Br) . . . . . . . . . . . . . . . . . . . . . . . 0.01% Chlorate and nitrate (as NO3). . . . . . . . . . . . . 0.003% Phosphate (PO4) . . . . . . . . . . . . . . . . . . . . . 5 ppm Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Barium (Ba) . . . . . . . . . . . . . . . . . . . . . . . . Passes test Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 5 ppm Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 3 ppm

© 2017 American Chemical Society

A

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

DOI:10.1021/acsreagents.4283 ACS Reagent Chemicals, Part 4

ACS Reagent Chemicals

Monograph

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

Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.002% Magnesium (Mg) . . . . . . . . . . . . . . . . . . . . . 0.001% Sodium (Na) . . . . . . . . . . . . . . . . . . . . . . . . 0.005%

TESTS Assay


(By argentimetric titration of chloride content). Weigh accurately about 0.3 g, and dissolve in 50 mL of water in a 250 mL glass-stoppered flask. Add 1 mL of dichlorofluorescein indicator solution. While stirring, mix and titrate with 0.1 N silver nitrate volumetric solution. The silver chloride should flocculate, and the mixture should change to pink. One milliliter of 0.1 N silver nitrate corresponds to 0.007455 g of KCl.

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.

Iodide Dissolve 11 g in 50 mL of water. Prepare a control by dissolving 1 g of the sample and 0.2 mg of iodide ion (I) in 50 mL of water. To each solution, in a separatory funnel, add 2 mL of hydrochloric acid and 5 mL of 5% ferric chloride reagent solution. Allow to stand for 5 min. Add 10 mL of chloroform, shake for 1 min, and allow the layers to separate. Any violet color in the chloroform layer in the sample should not exceed that of the control.

Bromide Dissolve 0.10 g of sample in 5.0 mL of water. Add 2.0 mL of pH 4.7 phenol red indicator solution, then add 1.0 mL of chloramine-T reagent solution, and stir immediately. After 2 min, add 0.15 mL of 0.1 N sodium thiosulfate volumetric solution, stir, and dilute to 10.0 mL with water. Simultaneously, set up a control solution by using 5.0 mL of potassium bromide (KBr) standard solution and adding the same quantity of reagents, carried out similarly in the same order as the sample solution, and dilute to 10.0 mL with water. The absorbance of the sample solution at 590 nm should not exceed that of the control solution, using water as the blank.

Chlorate and Nitrate

For the Determination of Chlorate and Nitrate

S a m p l e S o l u t i o n A . Dissolve 0.50 g in 3 mL of water by heating in a boiling water bath. Dilute to 50 mL with brucine sulfate reagent solution.


B




Monograph


C o n t r o l S o l u t i o n B . Dissolve 0.50 g in 1.5 mL of water and 1.5 mL of nitrate ion (NO3) standard solution by heating in a boiling water bath. Dilute to 50 mL with brucine sulfate reagent solution. B l a n k S o l u t i o n C . Use 50 mL of brucine sulfate reagent solution.

Heat the three solutions in a preheated (boiling) water bath for 10 min. Cool rapidly in an ice bath to room temperature. Set a spectrophotometer at 410 nm, and using 1 cm cells, adjust the instrument to read 0 absorbance with blank solution C in the light path, then determine the absorbance of sample solution A. Adjust the instrument to read 0 absorbance with sample solution A in the light path and determine the absorbance of control solution B. The absorbance of sample solution A should not exceed that of control solution B.


Phosphate [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 1 (Direct Molybdenum Blue)]. Dissolve 4.0 g in 25 mL of approximately 0.5 N sulfuric acid, and continue as described.

Sulfate Dissolve 25.0 g in 200 mL of water, add 2 mL of hydrochloric acid, heat to boiling, add 10 mL of 12% barium chloride reagent solution, digest in a covered beaker on a hot plate (~100 °C) for 2 h, and allow to stand for at least 8 h. If a precipitate is formed, filter, wash thoroughly, and ignite. Correct for the weight of barium sulfate obtained in a complete blank test.

Barium Dissolve 4.0 g in 20 mL of water, filter if necessary, and divide into two portions. To one portion, add 2 mL of 10% sulfuric acid reagent solution and to the other, 2 mL of water. The solutions should be equally clear at the end of 2 h. (Limit about 0.001%.)

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 1 (Ammonium Thiocyanate)]. Use 3.3 g.

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

For the Determination of Calcium, Magnesium, and Sodium

S a m p l e S t o c k S o l u t i o n . Dissolve 5.0 g of sample in water, and dilute to the mark with water in a 100 mL volumetric flask (1 mL = 0.05 g).


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Monograph


For the Determination of Calcium, Magnesium, and Sodium

Element

Wavelength (nm)

Sample Wt (g)

Standard Added (mg)

Flame Type*

Background Correction

Ca

422.7

1.0

0.02; 0.04

N/A

No

Mg

285.2

1.0

0.01; 0.02

A/A

Yes

Na

589.0

0.10

0.005; 0.01

A/A

No


*A/A is air/acetylene; N/A is nitrous oxide/acetylene.


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Potassium Chloride - ACS Reagent Chemicals (ACS Publications)

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