Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Potassium Hydroxide 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 Hydroxide 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, Potassium Carbonate, Chloride, Nitrogen Compounds, Phosphate, Sulfate, Heavy Metals, Iron, Nickel, Calcium, Magnesium, and Sodium.
KOH
Formula Wt 56.11
CAS No. 1310-58-3
Note: Reagent potassium hydroxide usually contains 10–15% water.
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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white, deliquescent solid alkalimetric titrations melting point, 360 °C 11 g in 100 mL at 20 °C
SPECIFICATIONS Assay and potassium carbonate . . . . . . . . . . . ≥85% KOH and ≤2.0% K2CO3 Maximum Allowable Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.01% Nitrogen compounds (as N) . . . . . . . . . . . . . . 0.001% Phosphate (PO4) . . . . . . . . . . . . . . . . . . . . . 5 ppm Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.003% Heavy metals (by ICP–OES) . . . . . . . . . . . . . . 0.001% Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.001% Nickel (Ni) . . . . . . . . . . . . . . . . . . . . . . . . . 0.001%
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4293 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Magnesium (Mg) . . . . . . . . . . . . . . . . . . . . . 0.002% Sodium (Na) . . . . . . . . . . . . . . . . . . . . . . . . 0.05%
TESTS Note: Special care must be taken in sampling to obtain a representative sample and to avoid absorption of water and carbon dioxide by the sample taken.
Assay and Potassium Carbonate (By acid–base titrimetry). Weigh rapidly 35–40 g to within 0.1 g, dissolve, cool, and dilute to 1 L with water. Dilute 50.0 mL of the well-mixed solution to 200 mL with water, add 5 mL of 12% barium chloride reagent solution, shake, and allow to stand for a few minutes. Titrate with 1 N hydrochloric acid volumetric solution to the phenolphthalein end point. One milliliter of 1 N hydrochloric acid corresponds to 0.05611 g of KOH. Continue the titration with 1 N hydrochloric acid to the methyl orange end point to determine carbonate. One milliliter of 1 N hydrochloric acid corresponds to 0.06911 g of K2CO3.
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For the Determination of Chloride, Nitrogen Compounds, Phosphate, Sulfate, Heavy Metals, Iron, and Nickel
S a m p l e S o l u t i o n A . Dissolve 50.0 g in carbon dioxide- and ammonia-free water, cool, and dilute with water to 500 mL in a volumetric flask (1 mL = 0.10 g).
Chloride† [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 1.0 mL of sample solution A (0.1 g sample).
Nitrogen Compounds† [Part 2: Colorimetry and Turbidimetry; Nitrogen Compounds: Test for Ammonia, Amines, and Nitrogen Compounds Reduced by Aluminum]. Use 20 mL of sample solution A (2 g sample). For the control, use 10 mL of sample solution A and 0.01 mg of nitrogen ion (N).
Phosphate† [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 1 (Direct Molybdenum Blue)]. To 40 mL of sample solution A (4 g sample), add 10 mL of hydrochloric acid, and evaporate to dryness on a hot plate (~100 °C). Dissolve the residue in 25 mL of approximately 0.5 N sulfuric acid, and continue as described. For the standard, include the residue from evaporation of 5 mL of hydrochloric acid.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4293 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
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Sulfate
[Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 1]. Neutralize 16.7 mL of sample solution A, and evaporate to 10 mL. Allow 30 min for turbidity to form.
Heavy Metals† ([Part 2: Trace and Ultratrace Elemental Analysis; Inductively Coupled Plasma−Optical Emission Spectroscopy (ICP–OES); Calculation of Heavy Metals (by ICP–OES) Results], by ICP–OES). Use 1.0 g sample.
Iron† [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Neutralize 10 mL of sample solution A (1 g sample) with hydrochloric acid, using phenolphthalein indicator. Add 2 mL in excess, and dilute with water to 50 mL. Use this solution. For the standard, use the residue obtained by evaporating the quantity of acid used to neutralize the sample solution.
Nickel† Dilute 20 mL of sample solution A (2 g sample) to 50 mL with water and neutralize with hydrochloric acid. Dilute with water to 85 mL and adjust the pH to 8 with ammonium hydroxide. Add 5 mL of bromine water, 5 mL of 1% dimethylglyoxime reagent solution, and 5 mL of 10% sodium hydroxide reagent solution. Any red color should not exceed that produced by 0.02 mg of nickel in an equal volume of solution containing the quantities of reagents used in the test.
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 . Using an ice-water bath, cautiously dissolve 10.0 g of sample in 50 mL of water, cool to about 15 °C, and slowly add 40 mL of nitric acid (1:1) with stirring. Cool to room temperature, transfer to a 100 mL volumetric flask, dilute to the mark with water, and mix (1 mL = 0.10 g).
For the Determination of Calcium, Magnesium, and Sodium
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Ca
422.7
2.0
0.05; 0.10
N/A
No
Mg
285.2
0.50
0.005; 0.01
A/A
Yes
Na
589.0
0.05
0.02; 0.04
A/A
No
*A/A is air/acetylene; N/A is nitrous oxide/acetylene.
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DOI:10.1021/acsreagents.4293 ACS Reagent Chemicals, Part 4
