Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Sodium Carbonate (Sodium Carbonate, Anhydrous) 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 Carbonate 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, Insoluble Matter, Loss on Heating at 285 °C, Chloride, Phosphate, Silica, Sulfur Compounds, Heavy Metals, Iron, Calcium, Magnesium, and Potassium.
Na2CO3
Formula Wt 105.99
CAS No. 497-19-8
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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white solid buffers; pH adjustment melting point, 851 °C 21.5 g in 100 mL at 20 °C
SPECIFICATIONS Assay (dried basis). . . . . . . . . . . . . . . . . . . . ≥99.5% Na2CO3 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.01% Loss on heating at 285 °C . . . . . . . . . . . . . . . 1.0% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Phosphate (PO4) . . . . . . . . . . . . . . . . . . . . . 0.001% Silica (SiO2) . . . . . . . . . . . . . . . . . . . . . . . . 0.005% Sulfur compounds (as SO4). . . . . . . . . . . . . . . 0.003% Heavy metals (by ICP–OES) . . . . . . . . . . . . . . 5 ppm Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ppm Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.03%
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4336 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Magnesium (Mg) . . . . . . . . . . . . . . . . . . . . . 0.005% Potassium (K) . . . . . . . . . . . . . . . . . . . . . . . 0.005%
TESTS Assay (By acid–base titrimetry of carbonate). Weigh, to the nearest 0.1 mg, about 2 g of the dried sample from the test for loss on heating at 285 °C. Transfer to a 125 mL glass-stoppered flask, dissolve with 50 mL of water, add 0.10 mL of methyl orange indicator solution, and titrate with 1 N hydrochloric acid volumetric solution. One milliliter of 1 N hydrochloric acid corresponds to 0.053 g of Na2CO3.
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 10 g dissolved in 100 mL of water.
Loss on Heating at 285 °C Crush sample, and accurately weigh 10 g in a preconditioned, low-form weighing bottle. Heat to constant weight at 270–300 °C. Retain this sample for assay determination.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 1.0 g of sample and 2 mL of nitric acid.
Phosphate [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 2 (Extracted Molybdenum Blue)]. Dissolve 1.0 g in 50 mL of water in a platinum dish, and digest on a hot plate (~100 °C) for 30 min. Cool, neutralize with dilute sulfuric acid (1:19) to a pH of about 4, and dilute with water to about 75 mL. Add 0.5 g of ammonium molybdate, and adjust the pH to 1.8 (using a pH meter) with dilute hydrochloric acid (1:9). Heat to boiling, cool, add 10 mL of hydrochloric acid, and dilute with water to 100 mL. Continue as described, and concurrently prepare a standard containing 0.01 mg of phosphate ion (PO4) and 0.05 mg of silica ion (SiO2) in about 75 mL of water treated as the 75 mL of sample solution. Reserve the aqueous phase for the determination of silica.
Silica Add 10 mL of hydrochloric acid to the solutions reserved from the determination of phosphate, and transfer to separatory funnels. Add 40 mL of butyl alcohol, shake vigorously, and allow to separate. Draw off and discard the aqueous phase. Wash the butyl alcohol three times with 20 mL portions of dilute hydrochloric acid (1:99), discarding the washings each time. Dilute each butyl alcohol solution with butyl alcohol to 50 mL, take 10 mL from each, and dilute each to 50 mL with butyl alcohol. Add 0.5 mL of a freshly prepared 2% stannous chloride reagent solution. The blue color in the extract from the sample should not exceed that in the standard. If the butyl alcohol extracts are turbid, wash with 10 mL of dilute hydrochloric acid (1:99).
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4336 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Sulfur Compounds To prepare the sample solution, dissolve 2.0 g of sample in 20 mL of water, evaporate to 5 mL, add 1 mL of bromine water, and evaporate to dryness. Cool. Dissolve in 10 mL of 10% hydrochloric acid, and evaporate to dryness. Cool. Add 5 mL of 10% hydrochloric acid, and evaporate to dryness. Cool. Dissolve with 10 mL of water and evaporate to dryness. Cool. Dissolve in 10 mL of water, adjust the pH to approximately pH 2 with 10% hydrochloric acid or dilute ammonium hydroxide (1:3). Filter through a washed, fine-porosity filter paper, wash with two 2 mL portions of water, and dilute with water to 20 mL. To prepare the standard solution, take 6 mL of sulfate ion (SO4) standard solution, and add 1 mL of dilute hydrochloric acid (1:19). Dilute with water to 20 mL. To the sample and standard solutions, add 1 mL of 12% barium chloride reagent solution and allow to stand 30 min. Any turbidity in the sample solution must not exceed that of the standard.
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 2.0 g sample
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 + 9). 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 with 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
0.10
0.03; 0.06
N/A
No
Mg
285.2
0.10
0.005; 0.01
A/A
Yes
K
766.5
0.20
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.4336 ACS Reagent Chemicals, Part 4
