Lithium Tetraborate - American Chemical Society

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

Lithium Tetraborate 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

Downloaded by NEW YORK UNIV on May 18, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4200

ABSTRACT This monograph for Lithium Tetraborate provides, in addition to common physical constants, a general description including typical appearance, applications, 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, Bulk Density, Insoluble Matter, Loss on Fusion at 950 °C, Phosphorus Compounds, Silicon, Aluminum, Calcium, Iron, Magnesium, Potassium, Sodium, and Heavy Metals.

Li2B4O7

Formula Wt 169.11

CAS No. 12007-60-2

Suitable for use in X-ray spectroscopy. Note: The formula weight of this reagent is likely to deviate from the value cited because the natural distribution of 6 Li and 7Li isotopes is often altered in current sources of lithium compounds.

GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . white solid Applications . . . . . . . . . . . . . . . . . . . . . . . . flux Aqueous solubility . . . . . . . . . . . . . . . . . . . . sparingly soluble

SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98.0–102.0% Li2B4O7 Bulk density . . . . . . . . . . . . . . . . . . . . . . . . ≥0.25 g/mL Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.01% Loss on fusion at 950 °C . . . . . . . . . . . . . . . . 2.0% Phosphorus compounds (as PO4) . . . . . . . . . . . 0.004% Silicon (Si) . . . . . . . . . . . . . . . . . . . . . . . . . 0.01% Aluminum (Al) . . . . . . . . . . . . . . . . . . . . . . 0.001%

© 2017 American Chemical Society

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

DOI:10.1021/acsreagents.4200 ACS Reagent Chemicals, Part 4

ACS Reagent Chemicals

Monograph

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

Calcium (Ca) . . . . . Iron (Fe) . . . . . . . . Magnesium (Mg) . . . Potassium (K) . . . . . Sodium (Na) . . . . . . Heavy metals (as Pb)

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0.01% 0.001% 5 ppm 0.005% 0.005% 0.001%

TESTS


Assay (By acidimetry). Weigh accurately about 1 g, dissolve in 80 mL of water in a 125 mL conical flask, and heat to boiling. Cool to room temperature, add 0.15 mL of 0.1% bromphenol blue indicator solution, and titrate with 1 N hydrochloric acid volumetric solution until the first appearance of yellow. One milliliter of 1 N hydrochloric acid corresponds to 0.08456 g of Li2B4O7.

where L = % loss on fusion at 950 °C.

Bulk Density Weigh a dry 50 mL glass-stoppered cylinder, calibrated to contain, then add approximately 50 mL of sample. Stopper, and reweigh to the nearest 0.1 g. Grasp the cylinder above its base, and from a height of 1 inch, lower the base sharply against a No. 12 rubber stopper. Level the surface of the powder with a gentle back and forth motion of the cylinder in mid-air. Record the volume. Repeat two more times, starting with the rotation of the cylinder. Use the mean of the three volume readings to calculate the apparent density.

Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 10 g dissolved in 400 mL of water.

Loss on Fusion at 950 °C Heat 1 g, accurately weighed, in a preconditioned platinum crucible or dish at 950 °C for 15 min.

Phosphorus Compounds Dissolve 5.0 g in 40 mL of dilute nitric acid (1:1), and evaporate on a steam bath to a syrupy residue. Dissolve the residue in about 80 mL of water, dilute with water to 100 mL, and dilute 20 mL of this solution with water to 100 mL. For the test, dilute 10 mL (0.1 g sample) with water to 70 mL. Prepare a standard containing 0.01 mg of phosphate ion (PO4) in 70 mL of water. To each solution, add 5 mL of ammonium molybdate reagent solution, and adjust the pH to 1.8 (using a pH meter) by adding dilute hydrochloric acid (1:1) or dilute ammonium hydroxide (1:1). Cautiously heat the solutions to near boiling but do not boil, then cool to room temperature. If a precipitate forms, it will dissolve when the solution is acidified in the next steps. To each solution, add 10 mL of hydrochloric acid, and dilute each with water to 100 mL. Transfer the solutions to separatory funnels, add 35 mL of ethyl ether to each, shake vigorously, and allow to separate. Draw off and discard the aqueous phases. Wash the ether phases twice with 10 mL portions of dilute hydrochloric acid (1:9), and discard the washings each time. To the washed ether phases, add 10 mL of dilute hydrochloric acid (1:9), to which has been added 0.2 mL of a freshly prepared 2% stannous chloride reagent solution. Shake the solutions, and allow the phases to separate. Any blue color in the ether phase from the solution of the sample should not exceed that in the ether phase from the standard.


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Silicon Fuse 1.00 g at 950 °C for 15 min in a 15 mL platinum crucible. Remove the crucible from the furnace, swirl to spread the melt around the sides of the crucible, and cool. Add a small magnetic stirring bar to the crucible, stir while adding 6.0 mL of 3 N hydrochloric acid, and stir until the melt disintegrates. Transfer the slurry with 50 mL of water to a 150 mL beaker. Adjust the pH to 2.0 ± 0.2 (using a pH meter) with 0.06 N hydrochloric acid (or dilute ammonium hydroxide). The solution should be clear at the final pH adjustment. Add 2.0 mL of ammonium molybdate solution (described below), mix, and let stand for 10 min. Add 4.0 mL of tartaric acid reagent solution, then 1.0 mL of reducing solution (described below). Mix the solution after each addition. Finally, dilute the solution with water to 100 mL. After 30 min, the blue color should not exceed that produced by 0.21 mg of silica in an equal volume of solution containing 10.0 mL of 0.06 N hydrochloric acid, 50 mL of water, and the quantities of reagents used in the test. If desired, the absorbances can be measured with a spectrophotometer at 650 nm, using water as a reference.


For the Determination of Silicon

A m m o n i u m M o l y b d a t e S o l u t i o n . Dissolve 7.5 g of ammonium molybdate tetrahydrate in 75 mL of water. Add 10.0 mL of 18 N sulfuric acid, dilute with water to 100 mL, filter, and store in a plastic bottle. Re d u c i n g S o l u t i o n . Dissolve 0.7 g of sodium sulfite in 20 mL of water, then dissolve into this solution 0.15 g of 4amino-3-hydroxy-1-naphthalene sulfonic acid. Add with constant stirring a solution of 9 g of sodium bisulfite in 80 mL of water. Filter the resulting solution into a plastic bottle. Discard after 3 days.

Aluminum Add 25 mL of methanol and 1.8 mL of hydrochloric acid to 1.0 g in a 100 mL plastic beaker. Evaporate to dryness on a hot plate (~100 °C), add 15 mL of methanol and 0.3 mL of hydrochloric acid, and evaporate again to dryness. Add another 15 mL of methanol and 0.3 mL of hydrochloric acid, repeat the evaporation, and dissolve the residue in 15.0 mL of 0.06 N hydrochloric acid. Transfer the solution of the sample to a 100 mL volumetric flask with 45 mL of water. For the blank and the standard, respectively, add 15.0 mL of 0.06 N hydrochloric acid to two 100 mL volumetric flasks containing 0 and 10 µg of aluminum, then add 45 mL of water. To each of the three flasks add 5.0 g of lithium chloride reagent solution, 1.0 mL of hydroxylamine hydrochloride reagent solution, and 4.0 mL of ascorbic acid reagent solution. Mix and let stand for 5 min. Add 10.0 mL of sodium acetate–acetic acid buffer solution (described below), mix, and let stand for 10 min. Add 5.0 mL of alizarin red S reagent solution, and dilute with water to 100 mL. The final pH should be 4.6 ± 0.1 (using a pH meter). After 1 h,measure the absorbance of the sample and the standard at 500 nm in 5 cm cells with the blank as the reference. The absorbance of the sample should not exceed that of the standard.

For the Determination of Aluminum

S o d i u m A c e t a t e – A c e t i c A c i d B u f f e r S o l u t i o n . Dissolve 100 g of sodium acetate trihydrate in water. Add 30 mL of glacial acetic acid, and dilute with water to 500 mL. Filter if necessary.

Calcium, Iron, Magnesium, Potassium, 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, Iron, Magnesium, Potassium, and Sodium

S a m p l e S t o c k S o l u t i o n a n d B l a n k S o l u t i o n . Weigh 10 g of sample into a 2 L beaker, add 400 mL of methanol and 5 mL of hydrochloric acid, and evaporate to dryness. Repeat the evaporation using 200 mL of methanol and 2 mL of


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hydrochloric acid, then add 100 mL of methanol and 1 mL of hydrochloric acid, and perform a third evaporation. Prepare a blank in the same manner, using the quantities of reagents used for preparation of the sample. Dissolve each residue in 50 mL of water and 1 mL of hydrochloric acid, transfer to a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.1 g).


For the Determination of Calcium, Iron, Magnesium, Potassium, 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

Fe

248.3

1.0

0.01; 0.02

A/A

Yes

Mg

285.2

1.0

0.005; 0.01

A/A

Yes

K

766.5

1.0

0.05; 0.10

A/A

No

Na

589.0

0.10

0.005; 0.01

A/A

No

*A/A is air/acetylene; N/A is nitrous oxide/acetylene.

Heavy Metals Dilute 20 mL of glacial acetic acid with water to 80 mL, add 5.0 g of sample while stirring, and heat to about 80 °C to dissolve. Prepare a control with 1.0 g of sample, 5.0 mL of glacial acetic acid, and 0.04 mg of lead in a volume of 80 mL. The pH of the solutions should be between 3 and 4. Keep the solutions at 80 °C, add 10 mL of freshly prepared hydrogen sulfide water to each, and mix. Transfer to 100 mL Nessler tubes. Any color in the solution of the sample should not exceed that in the control. (If the solutions are permitted to cool, a white crystalline precipitate forms.)


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Lithium Tetraborate - American Chemical Society

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