ASTM D873 Oxidation Stability of Aviation Fuels (Potential Residue Method)
9. Preparation of Apparatus
9.1 Thoroughly clean a glass sample container to remove traces of any adhering material. Immerse the container and its cover in a mildly alkaline or neutral pH laboratory detergent cleaning solution. The type of detergent and conditions for its use need to be established in each laboratory. The criterion for satisfactory cleaning shall be a matching of the quality of that obtained with chromic acid cleaning solutions (or some other equivalently strong oxidizing non-chromium containing acid cleaning solutions) on used sample containers and covers (fresh chromic acid, 6-h soaking period, rinsing with distilled water and drying). For this comparison, visual appearance and mass loss on heating the glassware under test conditions may be used. Detergent cleaning avoids the potential hazards and inconveniences related to the handling of highly corrosive and strongly oxidizing acid solutions; this procedure remains the reference cleaning practice and, as such, may function as an alternate to the preferred procedure, cleaning with detergent solutions. Remove from the cleaning solution by means of corrosion-resistant steel forceps and handle only with forceps thereafter. Wash thoroughly first with tap water and then with deionized or distilled water, and dry in an oven at 100 to 150°C for 1 h. Cool the sample containers and covers for at least 2 h in the cooling vessel in the vicinity of the balance. Weigh to the nearest 0.1 mg, and record mass.
9.1.1 Experience indicates that the amount of insoluble gum is negligible in aviation reciprocating engine fuels. Therefore, the glass sample container need not be weighed when testing such fuels unless visible evidence of insoluble matter remains in the container after treatment with gum solvent. In such cases, the test must be repeated and the mass of the container recorded.
9.2 Drain any fuel from the pressure vessel and wipe the inside of the pressure vessel and pressure vessel closure, first with a clean cloth moistened with gum solvent and then with a clean, dry cloth. Remove the filler rod from the stem, and carefully clean any gum or fuel from the stem, rod, and needle valve with gum solvent. The pressure vessel, the valve, and all connecting lines shall be thoroughly dry before each test is started.
NOTE 8 - Caution: Volatile peroxides, which may have formed during a previous test, may accumulate in the equipment, producing a potentially explosive environment. Special care in cleaning after each test is needed to ensure that the filler rod, stem, and needle valve are free of these peroxides.
9.3 If a thermostatically controlled constant temperature oxidation bath is used, adjust the temperature to 100 +/- 0.1°C and maintain it within this temperature range for the duration of the test.
9.4 If a boiling water oxidation bath is used, adjust the temperature within the range from 99.5 to 100.5°C by the addition of water or a higher boiling liquid such as ethylene glycol. Factors are given in Table 1 to adjust the "X" hour aging time if the bath temperature at the start of the test deviates from 100°C.
