ASTM D612 Standard Test Method for Carbonizable Substances in Paraffin Wax
7. Procedure
7.1 Clean a test tube with cleaning solution of sulfuric acid and Nochromix (Warning - Nochromix is corrosive. See A1.1), rinse with tap water followed by distilled water, and dry in an oven at 105°C for 1 h.
7.2 Melt a representative portion of the sample on a steam bath or hot water bath. Fill the test tube to the 5-mL mark with H2SO4 (94.7 +/- 0.2 %). Then add the melted wax, at a temperature not more than 10°F (5.5°C) above its melting point, to the 10-mL mark, insert the stopper loosely, and place the test tube in position in the water bath at 158 +/- 1.0°F (70 +/- 0.5°C).
7.3 After the test tube has been in the water bath for 5 min, loosen the stopper sufficiently to release any pressure and reinsert, remove the test tube from the bath quickly, hold with a finger over the stopper, and give three vigorous, vertical shakes over an amplitude of about 5 in. (127 mm), shaking the test tube quickly and at a rate corresponding to 5 shakes/s. Repeat every minute. Do not keep the test tube out of the bath longer than 3 s for each shaking period.
NOTE 1 - A shaking machine may be used provided that the results obtained agree with those obtained by the prescribed manual agitation.
7.4 At the end of 10 min from the time the test tube was first placed in the bath, remove the test tube, immediately place it in the color comparator, and compare the acid layer with 5 mL of the standard colorimetric solution and 5 mL of white mineral oil in a test tube that has been shaken vigorously for 10 s and allowed to stand just long enough for the contents to separate into two layers.
7.5 In some cases the acid remains trapped with the wax as an emulsion, and no lower layer is obtained to compare with the standard colorimetric solution. When this occurs, compare the emulsion with the standard colorimetric solution and white mineral oil shaken vigorously to give a similar emulsion, and without waiting for the two liquids to separate.
