D482_8 (13)

Heat the evaporating dish or crucible that is to be used for the test at 700 to 800 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 or crucible is cooled can be a desiccator not containing a desiccating agent. In addition, all weighings of the crucibles should be performed as soon as the crucibles have cooled. If it should be necessary that the crucibles remain in the desiccator for a longer period, than all subsequent weighings should be made after allowing the crucibles and contents to remain in the desiccator for the same length of time. When the sample is sufficiently mobile, mix thoroughly before weighing. The mixing is necessary to distribute catalyzed finds and other particulate material throughout the sample. Satisfactory mixing can usually be achieved by 10 minutes of manual shaking or 10 minutes using a mechanical shaker. Examine the sample for homogeneity before proceeding with section 8.3 of the written standard. Continue mixing the sample, if it is not homogeneous. When it is evident that the sample is not homogenized after repeating mixings, or there is a reasonable doubt, a non-aerating, high-speed, shear mixer can be used. Such a device is described in annex A1 of Test Methods D4928. When the sample cannot be satisfactorily homogenized, reject the sample and acquire a new sample. When the sample is viscous or solid at room temperature, heat the container carefully until the sample is entirely liquid, and mix carefully. An oven at an appropriate temperature can be used. The sample can contain water. After heating in an oven, the water can boil, causing splattering or foaming. The operator shall proceed cautiously with the heating step, wearing appropriate personnel protective equipment, such as safety goggles and gloves. Mixing this type of sample shall be done carefully. Stirring, rather than shaking, in an option. The quantity of test specimen taken for testing will depend upon the ash content expected in the sample. Refer to Table 1 of the written standard. The weighing procedure will also depend upon whether the sample requires heating or not, and whether more than one portion has to be weighed. Using a top-loading balance, weigh into the dish or crucible sufficient test specimen to the nearest 0.1 grams to yield no more than 20 milligrams of ash. Determine the mass of the test specimen used in the analysis at ambient temperature. One way to do this is to take the difference between the initial and final masses of the sample container weighed at ambient temperatures. If one weighing is sufficient, as determined from Table 1 of the written standard or experience, proceed with steps 8.6 through 8.11. If more than one addition of test specimen is required, proceed only through 8.6, noting 8.6.1 and 8.7. And allow the dish or crucible to cool to ambient temperature before adding more sample as outlined in 8.4 of the written standard. Proceed with steps 8.6 through 8.11. Carefully heat the dish or crucible with a Meker burner or equivalent until the contents can be ignited by the flame. Maintain the dish or crucible at such a temperature that the sample continues to burn at a uniform and moderate rate, leaving only a carbonaceous residue when the burning ceases. A hotplate can be used at this stage. The test sample may contain water that can cause spattering. The operator shall heat the test portion cautiously, while wearing appropriate personnel protective equipment, such as safety goggles and gloves. If spattering is very severe, so that material escapes the confines of the dish or the crucible, discard the test portion. If the first test portion is discarded, add 2 plus or minus 1 milliliters of isopropyl alcohol-- warning, flammable-- to a second test portion while stirring with a glass rod and warming the test portion gently to liquefy it, if it is solid or near solid. Proceed as described in 8.6 of the written standard. If this is unsuccessful, repeat on a third test portion using a 10 plus or minus 1 milliliter mixture of 50 plus or minus 5% by volume toluene-- warning, flammable, vapor harmful-- and 50 plus or minus 5% by volume of isopropyl alcohol. In either case, any test specimen that adheres to the glass rod can be returned to the dish using a strip of ashless filter paper. Continue burning as outlined in 8.6 of the written standard. Vigilance by the operator is mandatory. Burning samples shall never be left unattended. Some test specimens will require extra heating after the burning has ceased, particularly heavy samples, such as marine fuels, which form crusts over the unburned material. The crust can be broken with a glass rod. Any crust that adheres to the glass rod can be returned to the dish using a strip of ashless filter paper. Burn the remaining test specimen. The heavier material tends to foam. Therefore, the operator shall exercise considerable care. Overheating shall be avoided, so that neither the test specimen nor the dish are heated to a red hot appearance, as this can result in loss of ash. Likewise, the flame shall never be higher than the rim of the dish to avoid super heating the crust, thereby producing sparks that can result in considerable loss of ash. Heat the residue in the muffle furnace at 775 plus or minus 25 degrees Celsius, until all carbonaceous material has disappeared. Cool the dish to room temperature in a suitable container, as referenced in Note 4 of the written standard, and weigh to the nearest 0.1 milligrams. Reheat the dish at 775 plus or minus 25 degrees Celsius for at least 20 minutes. Cool in a suitable container as referenced in Note 4 of the written standard, and reweigh. Repeat the heating, cooling, and weighing process until consecutive weighings differ by not more than 0.5 milligrams.