Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Boric Acid 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
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ABSTRACT This monograph for Boric Acid provides, in addition to common physical constants, a general description including typical appearance, applications, change in state (approximate), aqueous solubility, and pKa. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, Insoluble in Methanol, Nonvolatile with Methanol, Chloride, Phosphate, Sulfate, Heavy Metals, Iron, and Calcium.
H3BO3
Formula Wt 61.83
CAS No. 10043-35-3
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . . pKa . . . . . . . . . . . . . . . . . .
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colorless or white solid primary standard; buffer melting point, 171 °C 5 g in 100 mL at 21 °C 9.2
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.5% H3BO3
Insoluble in methanol. . . . Nonvolatile with methanol Chloride (Cl) . . . . . . . . . Phosphate (PO4) . . . . . . . Sulfate (SO4) . . . . . . . . . Heavy metals (as Pb) . . . .
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© 2017 American Chemical Society
Maximum Allowable 0.005% 0.05% 0.001% 0.001% 0.01% 0.001%
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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4059 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.001% Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.005%
TESTS Assay
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(By acid–base titrimetry). Weigh, to the nearest 0.1 mg, 2.5 g of sample, and transfer to a 250 mL glass-stoppered flask. Dissolve in a mixture of 50 mL of water and 75 mL of glycerol, previously neutralized to a pH of 9.0 with 0.1 N sodium hydroxide, using a pH meter. Titrate with 1 N sodium hydroxide volumetric solution to a pH of 9.0. One milliliter of 1 N sodium hydroxide corresponds to 0.06183 g of H3BO3.
Insoluble in Methanol Heat 20 g with 200 mL of methanol under complete reflux until the acid is dissolved, then reflux for 30 min. Filter through a tared, preconditioned filtering crucible, wash thoroughly with hot methanol, and dry at 105 °C.
Nonvolatile with Methanol To 2.0 g of the sample in a platinum dish, add 25 mL of methanol and 0.5 mL of hydrochloric acid, and evaporate to dryness. Repeat the evaporation twice, each with 15 mL of methanol and 0.3 mL of hydrochloric acid. Add to the residue 0.10 mL of sulfuric acid, and ignite at 600 ± 25 °C for 15 min.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 1.0 g dissolved in 20 mL of warm water.
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For the Determination of Phosphate, Sulfate, Heavy Metals, and Iron
S a m p l e S o l u t i o n A . To 10 g, add 10 mg of sodium carbonate, 100 mL of methanol, and 5 mL of hydrochloric acid. Digest in a covered beaker on a hot plate (~100 °C) to effect dissolution, then uncover, and evaporate to dryness. Add 75 mL of methanol and 5 mL of hydrochloric acid, and repeat the digestion and evaporation. Dissolve the residue in 5 mL of 1 N acetic acid, and digest in a covered beaker on a hot plate (~100 °C) for 15 min. Filter, and dilute with water to 100 mL (1 mL = 0.1 g).
Phosphate† [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 1 (Direct Molybdenum Blue)]. Add 0.5 mL of nitric acid to 20 mL of sample solution A (2 g sample), and evaporate to dryness. Dissolve the residue in 25 mL of approximately 0.5 N sulfuric acid, and continue as described.
© 2017 American Chemical Society
B
ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4059 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
†
Sulfate
[Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 1]. Use 5.0 mL of sample solution A (0.5 g sample).
Heavy Metals† [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dilute 20 mL of sample solution A (2 g sample) with water to 25 mL.
Iron†
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[Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Use 10 mL of sample solution A (1 g sample).
Calcium (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).
For the Determination of Calcium
S a m p l e S t o c k S o l u t i o n . To 20 g, add 20 mg of sodium carbonate, 200 mL of methanol, and 10 mL of hydrochloric acid. Digest in a covered beaker on a hot plate (~100 °C) to effect solution, then uncover, and evaporate to dryness. Add 75 mL of methanol and 5 mL of hydrochloric acid, and repeat the digestion and evaporation. Dissolve the residue in 5 mL of 1 N acetic acid, and digest in a covered beaker on a hot plate (~100 °C) for 15 min. Filter, and dilute with water to volume in a 200 mL volumetric flask (1 mL = 0.1 g).
For the Determination of Calcium
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Ca
422.7
1.0
0.05; 0.10
N/A
No
*N/A is nitrous oxide/acetylene.
© 2017 American Chemical Society
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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4059 ACS Reagent Chemicals, Part 4
