Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Potassium Bicarbonate (Potassium Hydrogen Carbonate) 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 Bicarbonate provides, in addition to common physical constants, a general description including typical appearance and applications. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, Insoluble Matter, Chloride, Phosphate, Sulfur Compounds, Ammonium, Heavy Metals, Iron, Calcium, Magnesium, and Sodium.
KHCO3
Formula Wt 100.11
CAS No. 298-14-6
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . colorless or white solid Applications . . . . . . . . . . . . . . . . . . . . . . . . buffer
SPECIFICATIONS Assay (dried basis). . . . . . . . . . . . . . . . . . . . 99.7–100.5% KHCO3 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.01% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Phosphate (PO4) . . . . . . . . . . . . . . . . . . . . . 5 ppm Sulfur compounds (as SO4). . . . . . . . . . . . . . . 0.003% Ammonium (NH4) . . . . . . . . . . . . . . . . . . . . 5 ppm Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 5 ppm Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ppm Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.002% Magnesium (Mg) . . . . . . . . . . . . . . . . . . . . . 0.001% Sodium (Na) . . . . . . . . . . . . . . . . . . . . . . . . 0.03%
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4276 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By acid–base titrimetry). Weigh accurately 3.0 g, previously dried over sulfuric acid for 24 h, dissolve it in 50 mL of water, add 0.15 mL of methyl orange indicator solution, and titrate with 1 N hydrochloric acid volumetric solution. The potassium bicarbonate content calculated from the total alkalinity, as determined by the titration, should not be less than 99.7% nor more than 100.5% of the weight taken. One milliliter of 1 N hydrochloric acid corresponds to 0.1001 g of KHCO3.
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Dissolve 10 g in 100 mL of hot water, heat to boiling, and boil gently for 2–3 min.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 1.0 g.
Phosphate [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 1 (Direct Molybdenum Blue)]. Dissolve 4.0 g in 20 mL of water, add 5 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 proceed as described.
Sulfur Compounds [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 4]. Allow 30 min for turbidity to form.
Ammonium Dissolve 2.0 g in 40 mL of water, and add 10 mL of 10% sodium hydroxide reagent solution and 2 mL of Nessler reagent solution. Any color should not exceed that produced by 0.01 mg of ammonium ion in an equal volume of solution containing the quantities of reagents used in the test.
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. To 5.0 g in a 150 mL beaker, add 10 mL of water, mix, and add cautiously 10 mL of hydrochloric acid. Evaporate to dryness on a hot plate (~100 °C), dissolve the residue in about 20 mL of water, and dilute with water to 25 mL. For the control, add 0.02 mg of lead ion (Pb) to 1.0 g of sample, and treat exactly as the 5.0 g of sample.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Dissolve 2.0 g in 20 mL of water, cautiously add 5 mL of hydrochloric acid, and dilute with water to 50 mL. Use the solution without further acidification. In the standard, use only 3 mL of hydrochloric acid.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4276 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
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 . Cautiously dissolve 5.0 g of sample in 30 mL of dilute hydrochloric acid (1:2). Cool to room temperature, transfer to a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.05 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
1.0
0.02; 0.04
N/A
No
Mg
285.2
1.0
0.01; 0.02
A/A
Yes
Na
589.0
0.05
0.015; 0.03
A/A
No
*A/A is air/acetylene; N/A is nitrous oxide/acetylene.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4276 ACS Reagent Chemicals, Part 4
