Packaging and storage—
Preserve in well-closed containers.
Labeling—
Label powdered Pumice to indicate, in descriptive terms, the fineness of the powder.
Powdered Pumice meets the following requirements:
“Pumice Flour” or “Superfine Pumice”: not less than 97.0% of pumice flour or superfine pumice passes through a No. 200 standard mesh sieve.
“Fine Pumice”: not less than 95.0% of fine pumice passes through a No. 150 standard mesh sieve and not more than 75.0% passes through a No. 200 standard mesh sieve.
“Coarse Pumice”: not less than 95.0% of coarse pumice passes through a No. 60 standard mesh sieve and not more than 5.0% passes through a No. 200 standard mesh sieve.
Water-soluble substances—
Boil 10 g with 50 mL of water for 30 minutes, adding water from time to time to maintain approximately the original volume, and then filter: the filtrate is neutral to litmus, and one-half of this filtrate, when evaporated and dried at 105
for 1 hour, yields not more than 10 mg of residue (0.20%).
Acid-soluble substances—
Boil 1 g of Pumice with 25 mL of 3 N hydrochloric acid for 30 minutes, adding water from time to time to maintain approximately the original volume, then filter the liquid. Add 5 drops of sulfuric acid to the filtrate, evaporate to dryness, ignite, and weigh the residue: not more than 60 mg of residue is obtained (6.0%).
467
:
meets the requirements.