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D874_9 13a(2018)

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Select the size of the evaporating dish or crucible according to the quantity of sample necessary. See 9.3 of the written standard. Heat the evaporating dish or crucible that is used for the test at 775 degrees Celsius, plus or minus 25 degrees Celsius, for a minimum of 10 minutes. Cool to room temperature in a suitable container. And weigh to the nearest 0.1 milligrams. The container in which the dish is cooled does not contain a desiccating agent. Weigh into the dish a quantity of sample given as follows-- w equals 10 divided by a, where w equals mass of test specimen, g, grams, and a equals expected sulfated ash mass percent. However, do not take a quantity in excess of 80 grams. In the case of lubricating oil additives yielding a sulfated ash of 2% by mass or more, dilute the weighed sample in the dish with approximately 10 times its weight of low ash mineral oil. If the amount of sulfated ash found differs from the expected amount by more than a factor of 2, repeat the analysis with a different weight of sample calculated from the first analysis, unless the calculated sample size is greater than 80 grams. Heat the dish or crucible and sample carefully until the contents can be ignited with a flame. Maintain at such a temperature that the sample continues to burn at a uniform and moderate rate. When burning ceases, continue to heat gently until no further smoke or fumes are evolved. If the sample contains sufficient moisture to cause foaming and loss of material from the dish, discard the sample. And to an additional sample, add 1 milliliter to 2 milliliters of 99% isopropyl alcohol. Warning, flammable before heating. If this is not satisfactory, add 10 milliliters of a mixture of equal volumes of toluene-- warning, flammable, vapor harmful-- and isopropyl alcohol, and mix thoroughly. Place several strips of ashless filter paper in the mixture and heat. When the paper begins to burn, the greater part of the water will have been removed. Allow the dish to cool to room temperature, then completely moisten the residue by the dropwise addition of sulfuric acid, relative density 1.84. Carefully heat the dish at a low temperature on a hot plate or over a gas burner, avoiding spattering, and continue heating until fumes are no longer evolved. Place the dish in the furnace at 775 degrees Celsius, plus or minus 25 degrees Celsius for 30 minutes, plus or minus 5 minutes, until oxidation of the carbon is complete or almost complete. Allow the dish to cool to room temperature. Add 3 drops of water and 10 drops of sulfuric acid, 1 to 1 ratio. Move the dish so as to moisten the entire residue. Again, heat the dish in accordance with 9.5 of the written standard. Again, place the dish in the furnace at 775 degrees Celsius, plus or minus 25 degrees Celsius, and maintain at the temperature for 30 minutes, plus or minus 5 minutes. See note 8 of the written standard. Cool the dish to room temperature in a suitable container. See note 7 of the written standard. Zinc dialkyl or alkaryl dithiophosphates and blends containing these additives can give a residue that is particularly black at this stage. In this case, repeat 9.7 and 9.8 of the written standard until a white residue is obtained. A study conducted by two separate laboratories investigating whether heating sulfated ash residues for extended periods of time-- for example, overnight in a furnace at 775 degrees Celsius, plus or minus 25 degrees Celsius-- as opposed to 30 minutes as required in 9.8 of the written standard revealed that a significant difference in sulfated ash results can exist. The study indicated that lower sulfated ash results were obtained on the samples left in the furnace overnight versus those that were heated in 30-minute cycles. A thermogravimetric analysis also confirmed that the samples evaluated continued to lose weight at 775 degrees Celsius as a function of time. As such, it is essential that the 30-minute heating time requirement be adhered to in performing the test method. Details concerning the study can be found in ASTM Research Report RRD02-1597. Weigh the dish and residue to the nearest 0.1 milligrams. Repeat 9.8 and 9.9 of the written standard until two successive weighings differ by no more than 1.0 milligrams. Normally, one repeat will suffice, unless a high proportion of zinc is present, when three or four heating periods can be required. For samples expected to contain 0.02% mass or less of sulfated ash, determine a sulfuric acid blank by adding 1 milliliters of the concentrated sulfuric acid to a tared platinum dish or crucible, heating until fumes are no longer evolved, and then heating in the furnace at 775 degrees Celsius, plus or minus 25 degrees Celsius, for 30 minutes, plus or minus 5 minutes. Cool the dish or crucible to room temperature in a suitable container. See note 7 of the written standard. And weigh to the nearest 0.1 milligram. If any ash is found in the sulfuric acid, make an adjustment to the weight of sulfated ash obtained by subtracting the weight of ash contributed by the sulfuric acid, determined from the total volume of sulfuric acid used and the weight of ash found for the 1 milliliter blank from the total grams of sulfated ash for the sample. Use this corrected weight, w, in calculating the percent of sulfated ash.

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Posted by: abuckmaster on Sep 14, 2018

D874_9 13a(2018)

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