ASTM D4042 Test Method for Sampling and Testing for Ash and Total Iron in Steel Mill Dispersions of Rolling Oils
6. Ash Content
6.1 Apparatus:
6.1.1 Borosilicate-Glass Beaker, 400-mL, or Evaporating Dish, 350-mL, designed for ashing in an electric furnace. Do not use platinum crucibles because of the tendency to alloy with metallic iron.

6.1.2 Electric Muffle Furnace, capable of maintaining a temperature of 775 +/- 25°C (1427 +/- 45°F), preferably having suitable apertures at the front and rear that allow a slow natural draft of air to pass through.

6.1.3 Oven, capable of maintaining a temperature of 105 +/- 2°C (221 +/- 4°F).

6.1.4 Analytical Balance, 200-g capacity, accurate to 0.1 mg.

6.1.5 Top-Loading Balance, 600-g minimum capacity, accurate to 0.01 g.

6.2 Procedure:
6.2.1 Heat the empty beaker or evaporating dish at 700 to 800°C (1240 to 1470°F) for 10 min or more. Cool at room temperature in a suitable container (Note 5) and weigh on an analytical balance to the nearest 0.1 mg.

NOTE 5 - The container in which the beaker or evaporating dish is cooled should not contain a desiccating agent.

6.2.2 Remove the bagged sample from its carrier container and place it, still tied, in the dish. Remove the wire and weigh the bag with sample on a top loading balance to the nearest 0.01 g. Subtract the weight of the beaker or evaporating dish and record the weight in grams as WS1.

6.2.3 Place the beaker or dish, sample, and bag in an oven at 105°C (221°F) overnight or until the moisture has been evaporated from the sample.

6.2.4 Cover the beaker or evaporating dish with ashless filter paper (Note 6) to prevent loss due to spatter. Add this filter paper to the sample prior to ashing.

NOTE 6 - Filter paper should conform to Specification E 832, Type II.

6.2.5 Place the beaker or evaporating dish containing the dried sample, bag, and filter paper in the muffle furnace. Carefully heat the beaker or evaporating dish and sample by progressively advancing it into the muffle furnace where it will eventually ignite.
6.2.5.1 Maintain at such a temperature that the sample continues to burn at a uniform and moderate rate, leaving only ash and carbon when burning ceases.

NOTE 7 - Warning: Fumes from burning polyethylene are hazardous.

6.2.6 Heat the residue in the muffle furnace at 775 +/- 25°C (1427 +/- 45°F) until all carbonaceous material has disappeared.

6.2.7 Remove the dish and ashed sample from the furnace and cool in a suitable container to room temperature. Weigh on a 200-g analytical balance to the nearest 0.1 mg.

6.2.8 Reheat the dish to 775 +/- 25°C (1427 +/- 45°F) in the muffle furnace for 30 min, and cool to room temperature in a suitable container and reweigh, as in 6.2.6. Repeat the heating, cooling, and weighing until consecutive weighings differ by not more than 0.5 mg.

6.2.9 Subtract the weight of the evaporating dish (6.2.1) and record the final ash weight as WS2.

6.2.10 Place a new, empty polyethylene bag trimmed to the weight of the original sample bag +/- 0.01 g (5.2.2) in a preweighed evaporating dish (6.2.1) and reduce to ash following the procedure described by 6.2.4, 6.2.5, 6.2.6, 6.2.7, and 6.2.8.

6.2.11 Record the final ash weight in grams to the nearest 0.1 mg as WB2.

NOTE 8 - In repeat tests for duplicate samples or separate samples, if all sample bags used are from the same source and are of the same size, an average weight from three or more bags can be used for WB1. This avoids having to preweigh all bags as in 5.2.2. Also, the weight of the ashed empty bag WB2 can be used in subsequent calculations for ash determination. This avoids having to ash one sample bag for each duplicate or separate sample.

6.3 Calculation of Percent Ash - Calculate the weight of ash for the dispersion sample as a percentage of the original sample, as follows:
Ash, % = (WS2 - WB2)/(WS1 - WB1) x 100
where:
WS2 = ash from sample and bag, g,
WB2 = ash from empty bag, g,
WS1 = sample and bag, g, and
WB1 = bag, g.

NOTE 9 - Both the ash from the sample bag and the ash from the empty bag are to be used for subsequent total iron determination.