Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Sodium Acetate Trihydrate 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 Sodium Acetate Trihydrate 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, Substances Reducing Permanganate, Insoluble Matter, Chloride, Phosphate, Sulfate, Heavy Metals, Iron, Calcium, Magnesium, and Potassium.
NaC2H3O2 • 3H2O
Formula Wt 136.08
CAS No. 6131-90-4
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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colorless or white solid buffers melting point, 58 °C; dehydrates at 120 °C 125 g in 100 mL at 20 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99.0–101% NaC2H3O2 · 3H2O pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 7.5–9.2 Substances reducing permanganate . . . . . . . . . Passes test Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.005% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Phosphate (PO4) . . . . . . . . . . . . . . . . . . . . . 5 ppm Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.002% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 5 ppm Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ppm Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.005%
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4327 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Magnesium (Mg) . . . . . . . . . . . . . . . . . . . . . 0.002% Potassium (K) . . . . . . . . . . . . . . . . . . . . . . . 0.005%
TESTS Assay (Total alkalinity by nonaqueous titration). Weigh accurately about 0.5 g of sample into a 125 mL flask, and dissolve in 50 mL of acetic acid and 5 mL of acetic anhydride. Use a second flask containing 50 mL of acetic acid and 5 mL of acetic anhydride as a blank. Add 0.10 mL of crystal violet indicator solution to both flasks, and titrate with 0.1 N perchloric acid in glacial acetic acid volumetric solution until the solution color changes from violet to emerald green. One milliliter of 0.1 N perchloric acid corresponds to 0.01361 g of CH3COONa · 3H2O.
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].
Substances Reducing Permanganate Dissolve 5.0 g in 50 mL of water, and add 5 mL of 10% sulfuric acid reagent solution and 0.10 mL of 0.1 N potassium permanganate volumetric solution. The pink color should persist for at least 1 h.
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 20 g dissolved in 150 mL of water.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 1.0 g.
Phosphate [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 2 (Extracted Molybdenum Blue)]. Dissolve 2.0 g in 10 mL of nitric acid, and evaporate to dryness on a hot plate (~100 °C). Add 10 mL of nitric acid, and repeat the evaporation. Dissolve in 80 mL of water, add 0.5 g of ammonium molybdate tetrahydrate, and adjust the pH to 1.8 (using a pH meter) with dilute hydrochloric acid (1:9). Heat to boiling, cool, and add 10 mL of hydrochloric acid, and continue as described. Carry along a standard containing 0.01 mg of phosphate ion (PO4) treated in the same manner as the sample after the addition of 80 mL of water.
Sulfate [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 1]. Allow 30 min for turbidity to form.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4327 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dissolve 6.0 g in about 10 mL of water, add 15 mL of dilute hydrochloric acid (10%), and dilute with water to 30 mL. Use 25 mL to prepare the sample solution, and use 5.0 mL of the remaining solution to prepare the control solution.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Dissolve 2.0 g in 50 mL of dilute hydrochloric acid (1:24), and use the solution without further acidification.
Calcium, Magnesium, and Potassium (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 Potassium
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 in a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.05 g).
For the Determination of Calcium, Magnesium, and Potassium
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Ca
422.7
0.50
0.025; 0.05
N/A
No
Mg
285.2
0.50
0.01; 0.02
A/A
Yes
K
766.5
0.50
0.025; 0.05
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.4327 ACS Reagent Chemicals, Part 4
