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271
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Use a clean, dry, heat-resistant, glass-stoppered test tube, 140 ± 3 mm in length and 14 ± 1 mm in diameter, with a capacity of 16 ± 1 mL when the stopper is inserted, and calibrated at the 5- and 10-mL liquid levels. Place in the test tube 5 mL of Paraffin, at a temperature just above the melting point, add 5 mL of sulfuric acid containing 94.5% to 94.9% of H2SO4, and heat in a water bath at 70
for 10 minutes. When 5 minutes have elapsed, and at each successive minute thereafter, remove the tube from the bath, place a finger over the stopper, and give the tube three vigorous vertical shakes over an amplitude of about 12 cm, returning the tube to the bath within 3 seconds after the time when it was removed therefrom. At the end of 10 minutes from the time the tube was placed in the bath, the acid has no more color than a mixture of 3 mL of ferric chloride CS, 1.5 mL of cobaltous chloride CS, and 0.50 mL of cupric sulfate CS, overlaid with 5 mL of mineral oil. If the sulfuric acid remains dispersed in the molten paraffin, the color of the emulsion is not darker than that of the standard mixture when shaken vigorously.
467:
meets the requirements.