Sodium Borate Decahydrate - ACS Reagent Chemicals (ACS

Monograph pubs.acs.org/doi/book/10.1021/acsreagents

Sodium Borate Decahydrate (Borax, Sodium Tetraborate Decahydrate)

Downloaded by CORNELL UNIV on June 12, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4333

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 Borate Decahydrate 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 0.01 M Solution, Insoluble Matter, Chloride, Phosphate, Sulfate, Calcium, Heavy Metals, and Iron.

Na2B4O7 • 10H2O

Formula Wt 381.38

CAS No. 1303-96-4

GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . white solid Applications . . . . . . . . . . . . . . . . . . . . . . . . buffers; complexing or masking agent Change in state (approximate) . . . . . . . . . . . . melting point, when rapidly heated, at 75 °C; loses 5 H2O at 100 °C, 9 H2O at 150 °C; becomes anhydrous at 320 °C Aqueous solubility . . . . . . . . . . . . . . . . . . . . 1 g dissolves in 16 mL

SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99.5–105.0% Na2B4O7 · 10H2O pH of a 0.01 M solution. . . . . . . . . . . . . . . . . 9.15–9.20 at 25.0 °C Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.005% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Phosphate (PO4) . . . . . . . . . . . . . . . . . . . . . 0.001% Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 0.001% Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ppm

© 2017 American Chemical Society

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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.

DOI:10.1021/acsreagents.4333 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 about 1 g, and dissolve in 50 mL of water. Make slightly acidic to methyl red indicator with 1 N hydrochloric acid volumetric solution, cover with a watch glass, and boil gently for 2 min to expel any carbon dioxide. Cool, and adjust to the methyl red end point (pinkish yellow) with 1 N sodium hydroxide volumetric solution. Add phenolphthalein indicator solution and 8 g of mannitol, then titrate with 1 N sodium hydroxide through the development of a yellow color to a permanent pink end point. One milliliter of 1 N sodium hydroxide corresponds to 0.09536 g of Na2B4O7 · 10H2O. The pH adjustment may be done potentiometrically. The end points are pH 5.4 and 8.5.

pH of a 0.01 M Solution Dissolve 0.381 g in 100 g of carbon dioxide- and ammonia-free water (or 0.380 g in a volume of 100 mL). Standardize the pH meter and electrode at pH 9.18 at 25 °C with 0.01 M NIST SRM sodium tetraborate decahydrate prepared from NIST SRM. Determine the pH by the method described in [Part 2: Measurement of Physical Properties; Melting Point].

Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 20 g dissolved in 300 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 1 (Direct Molybdenum Blue)]. Dissolve 2.0 g in 10 mL of warm water, add 2 mL of hydrochloric acid, and evaporate to dryness on a hot plate (~100 °C). Dissolve in 25 mL of approximately 0.5 N sulfuric acid, filter to remove any boric acid, and use the clear filtrate. Continue as described.

Sulfate Dissolve 8.0 g in 120 mL of warm water plus 6 mL of hydrochloric acid. Filter, and wash with 30 mL of water. Heat to boiling, add 5 mL of 12% barium chloride reagent solution, digest in a covered beaker on a hot plate (~100 °C) for 2 h, and allow to stand for at least 8 h. Heat to dissolve any boric acid that may be crystallized. If a precipitate is formed, filter, wash thoroughly, and ignite. Correct for the weight obtained in a complete blank test.

Calcium (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).


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ACS Reagent Chemicals

Monograph

pubs.acs.org/doi/book/10.1021/acsreagents

For the Determination of Calcium

S a m p l e S t o c k S o l u t i o n . Dissolve 10.0 g of sample with water in a 200 mL volumetric flask, add 10 mL of hydrochloric acid, and dilute to the mark with water (1 mL = 0.05 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.

Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dissolve 4.0 g in 40 mL of hot water, add 5 mL of glacial acetic acid, and dilute with water to 48 mL. Use 36 mL to prepare the sample solution, and use the remaining 12 mL to prepare the control solution.

Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Use 2.0 g of sample and 3 mL of hydrochloric acid.


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Sodium Borate Decahydrate - ACS Reagent Chemicals (ACS

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