Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Potassium Sulfate 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 Sulfate 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, Chloride, Nitrogen Compounds, Heavy Metals, Iron, Calcium, Magnesium, and Sodium.
K2SO4
Formula Wt 174.25
CAS No. 7778-80-5
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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white or colorless solid Kjeldahl analysis melting point, 1069 °C 11 g in 100 mL at 20 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.0% K2SO4 pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 5–8.5 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.01% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Nitrogen compounds (as N) . . . . . . . . . . . . . . 5 ppm Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 5 ppm Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ppm Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.01% Magnesium (Mg) . . . . . . . . . . . . . . . . . . . . . 0.005% Sodium (Na) . . . . . . . . . . . . . . . . . . . . . . . . 0.02%
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4308 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By acid–base titrimetry). Weigh, to the nearest 0.1 mg, about 0.4 g of sample, and dissolve in 50 mL of water. Pass the solution through the cation-exchange column [Part 2: Titrimetric Methods; Ion-Exchange Column Assays; Method for IonExchange Column Assays] at a rate of about 5 mL/min, and collect the eluate in a 500 mL titration flask. Then, wash the resin in the column with water at a rate of about 10 mL/min, and collect in the same titration flask. Add 0.15 mL of phenolpthalein indicator solution to the flask, and titrate with 0.1 N sodium hydroxide. Continue the titration as the washing proceeds until 50 mL requires no further titration. One milliliter of 0.1 N sodium hydroxide corresponds to 0.008713 g of K2SO4.
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 10 g dissolved in 150 mL of water.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 1.0 g.
Nitrogen Compounds [Part 2: Colorimetry and Turbidimetry; Nitrogen Compounds: Test for Ammonia, Amines, and Nitrogen Compounds Reduced by Aluminum]. Use 2.0 g. For the standard, use 0.01 mg of nitrogen ion (N).
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dissolve 6.0 g in water, and dilute with water to 54 mL. Use 45 mL to prepare the sample solution, and use the remaining 9.0 mL to prepare the control solution.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Use 2.0 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 2.0 g of sample with water in a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.02 g).
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4308 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
For the Determination of Calcium, Magnesium, and Sodium
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Ca
422.7
0.20
0.02; 0.04
N/A
No
Mg
285.2
0.20
0.01; 0.02
A/A
Yes
Na
589.0
0.10
0.01; 0.02
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.4308 ACS Reagent Chemicals, Part 4
