ASTM D381 standard test method for gum content in fuels by jet evaporation
6. Apparatus
6.1 Balance, capable of weighing test specimens to the nearest 0.1 mg.
6.2 Beakers, of 100-mL capacity, as illustrated in Fig. 1. Arrange the beakers in sets, the number in each set depending upon the number of beaker wells in the evaporating bath. Mark each beaker in the set, including the tare beaker, with an identifying number or letter.
6.3 Cooling Vessel - A tightly covered vessel, such as a desiccator without desiccant, for cooling the beakers before weighing.
NOTE 1 - The use of a desiccant could lead to erroneous results.
6.4 Evaporation Bath (Warning - If a liquid-filled evaporation bath is used, care must be taken that the flash point of the liquid used is at least 30°C higher than the highest bath temperature expected.) Either a solid metal block bath or a liquid bath, electrically heated, and constructed in accordance with the general principles shown in Fig. 1 may be used. (Although all dimensions are given in SI units, older baths conforming to Test Method D381-94, or earlier, are suitable.) The bath should have wells and jets for two or more beakers. The rate of flow from each outlet when fitted with the conical adapters with 500 to 600 micron copper or stainless steel screens should not differ from 1000 mL/s by more than 15 %. A liquid bath, if used, shall be filled to within 25 mm of the top with a suitable liquid. Temperature shall be maintained by means of thermostatic controls or by refluxing liquids of suitable composition.
6.5 Flow Indicator, as illustrated in Fig. 1, such as a flowmeter, capable of metering a flow of air or steam equivalent to 1000 mL/s for each outlet.
NOTE 2 - Alternatively, a pressure gage may be used to meter the flow of air or steam equivalent to 1000 +/- 150 mL/s for each outlet.
6.6 Sintered Glass Filtering Funnel, coarse porosity, 150-mL capacity.
6.7 Steam - Supply by suitable means capable of delivering to the bath inlet the required amount of steam at 232 to 246°C.
6.8 Temperature Sensor, liquid-in-glass thermometer conforming to the requirements in the specification(s) for ASTM 3C/IP73C, found in Specification E 1, or another temperature measuring device or system, or both, of at least equivalent accuracy and precision over a temperature range from -5 to 400°C.
6.9 Graduated Cylinders, with spout, capable of measuring 50 +/- 0.5 mL.
6.10 Handling Equipment, forceps (stainless steel, spade ended) or tongs (stainless steel) for use in handling the beakers and conical jets, as required by this test method.
7. Materials
7.1 Air - Supply of filtered air at a pressure not more than 35 kPa.
7.2 Gum Solvent - A mixture of equal volumes of toluene and acetone.
7.3 Heptane - Minimum purity of 99.7 %.
7.4 Steam - Supply of steam free of oily residue and at a pressure not less than 35 kPa. (Warning - If a steam superheater is used, there may be exposed hot surfaces on the steam superheater. Avoid contact with exposed skin by use of protective equipment as required.)
