Packaging and storage—
Preserve in tight containers. Store at 25
, excursions permitted between 15
and 30
.
Loss on drying 
731
—
Dry it at 105
for 16 hours: it loses between 20.9% and 21.4% of its weight.
Insoluble matter—
Transfer 10 g to a 250-mL beaker, add 100 mL of water and 2 mL of hydrochloric acid, cover the beaker, and heat to boiling. Digest the hot solution on a steam bath for 1 hour, and filter through a tared, fine-porosity filtering crucible. Rinse the beaker with hot water, passing the rinsings through the filter, and finally wash the filter with additional hot water.
[NOTE—Retain the combined filtrate and washings for the test for
Sulfate.] Dry the filter at 105
: the residue weighs not more than 1.0 mg (0.01%).
Sulfate—
Heat to boiling the combined filtrate and washings retained from the test for
Insoluble matter, add 10 mL of
barium chloride TS, digest for 2 hours on a steam bath, and allow to stand overnight. Filter the solution through a tared, medium-porosity porcelain filtering crucible, and wash the residue with two 10-mL portions of hot water. Ignite at 800 ± 25
to constant weight: the weight of the residue, corrected for the weight obtained in a blank test, does not exceed 1.2 mg (0.005%).
Limit of sodium—
Stock solution—
Transfer 10.0 g of Cupric Chloride to a 100-mL volumetric flask, add water, and swirl to dissolve. Add 5 mL of nitric acid, dilute with water to volume, and mix. This solution contains 0.1 g of cupric chloride per mL.
Test solutions—
To three 25-mL volumetric flasks add a volume of Stock solution equivalent to the weight of test specimen given in the accompanying table. To two of the flasks add the amounts of reference analyte ion specified in the accompanying table. Add 2 mL of potassium chloride solution (1 in 20) to each flask, dilute with water to volume, and mix.
Procedure—
Using atomic absorption spectrophotometry (see
Spectrophotometry and Light-Scattering 851), analyze the
Test solutions by the method of standard addition analysis according to the accompanying table. The limit is 0.02%.
Limit of potassium—
Stock solution—
Use the Stock solution prepared in the test for Limit of sodium.
Test solutions—
To three 25-mL volumetric flasks add a volume of Stock solution equivalent to the weight of test specimen given in the accompanying table. To two of the flasks add the amounts of reference analyte ion specified in the accompanying table, dilute with water to volume, and mix.
Procedure—
Using atomic absorption spectrophotometry (see
Spectrophotometry and Light-Scattering 851), analyze the
Test solutions by the method of standard addition analysis according to the accompanying table. The limit is 0.01%.
Limit of calcium—
Stock solution—
Use the Stock solution prepared in the test for Limit of sodium.
Test solutions—
To three 25-mL volumetric flasks add a volume of Stock solution equivalent to the weight of test specimen given in the accompanying table. To two of the flasks add the amounts of reference analyte ion specified in the accompanying table, dilute with water to volume, and mix.
Procedure—
Using atomic absorption spectrophotometry (see
Spectrophotometry and Light-Scattering 851), analyze the
Test solutions by the method of standard addition analysis according to the accompanying table. The limit is 0.005%.
Limit of iron—
Stock solution—
Use the Stock solution prepared in the test for Limit of sodium.
Test solutions—
To three 25-mL volumetric flasks add a volume of Stock solution equivalent to the weight of test specimen given in the accompanying table. To two of the flasks add the amounts of reference analyte ion specified in the accompanying table, dilute with water to volume, and mix.
Procedure—
Using atomic absorption spectrophotometry (see
Spectrophotometry and Light-Scattering 851), analyze the
Test solutions by the method of standard addition analysis according to the accompanying table. The limit is 0.005%.
Limit of nickel—
Stock solution—
Use the Stock solution prepared in the test for Limit of sodium.
Test solutions—
To three 25-mL volumetric flasks add a volume of Stock solution equivalent to the weight of test specimen given in the accompanying table. To two of the flasks add the amounts of reference analyte ion specified in the accompanying table, dilute with water to volume, and mix.
Procedure—
Using atomic absorption spectrophotometry (see
Spectrophotometry and Light-Scattering 851), analyze the
Test solutions by the method of standard addition analysis according to the accompanying table. The limit is 0.01%.
Organic volatile impurities, Method IV 467:
meets the requirements.
Solvent—
Use dimethyl sulfoxide.
Assay—
Transfer about 400 mg of Cupric Chloride, accurately weighed, to a beaker, and dissolve in 50 mL of water. Add 4 mL of acetic acid and 3 g of potassium iodide, mix, and titrate the liberated iodine with 0.1 N sodium thiosulfate VS, adding about 2 g of potassium thiocyanate and 3 mL of
starch TS as the endpoint is approached. Each mL of 0.1 N sodium thiosulfate is equivalent to 13.45 mg of CuCl
2.
| Limit test |
Wavelength
(nm) |
Test specimen
weight (g) |
Reference ion
added (mg) |
Flame type |
Background
correction |
| Sodium |
589.0 |
0.1 |
0.01/0.02 |
air-acetylene |
No |
| Potassium |
766.5 |
0.1 |
0.01/0.02 |
air-acetylene |
No |
| Calcium |
422.7 |
2.0 |
0.05/0.10 |
air-acetylene |
No |
| Iron |
248.3 |
2.0 |
0.05/0.10 |
air-acetylene |
Yes |
| Nickel |
232.0 |
2.0 |
0.10/0.20 |
air-acetylene |
No |
