ASTM D4310 Method for Sludging and Corrosion Tendencies of Inhibited Mineral Oils
6. Apparatus
6.1 Oxidation Cell, of borosilicate glass, as shown in Fig. 1, consisting of a test tube, condenser, and oxygen delivery tube. The test tube has a calibration line at 300 mL (maximum error 1 mL). This calibration applies to the test tube without inserts at 20°C.

6.2 Heating Bath: Liquid Bath or Metal Block, thermostatically controlled, capable of maintaining the oil sample in the oxidation cell at a temperature of 95 ± 0.2°C, fitted with a suitable stirring device to provide a uniform temperature throughout the bath, and large enough to hold the desired number of oxidation cells immersed in the heating bath to a depth of 390 ± 10 mm and in the heating liquid itself to a depth of 355 ± 10 mm.
6.2.1 Studies have suggested that direct sunlight or artificial light may adversely influence the results of this test. To minimize effects of light exposure on the lubricant being tested, light shall be excluded from the lubricant by one or more of the following ways:
6.2.1.1 Use of heated liquid baths that are designed and constructed of metal, or combinations of metals and other suitable opaque materials, that prevent light from entering the test cell from the sides is preferred. If a viewing window is included in the design, this viewing window shall be fitted with a suitable opaque cover and be kept closed when no observation is being made.

6.2.1.2 If glass heating baths are used, the bath shall be wrapped with aluminum foil or other opaque material.

6.2.1.3 Bright light entering the test cell from directly overhead can be eliminated by use of an opaque shield.

6.3 Flowmeter, with a flow capacity of at least 3 L of oxygen/hour, and an accuracy of ± 0.1 L/h.

6.4 Heating Bath Thermometer - ASTM Solvents Distillation Thermometer having a range from 72 to 126°C and conforming to the requirements for Thermometer 40C as prescribed in Specification E1, or for Thermometer 70C as prescribed in Specifications for IP Standard Thermometers. Alternatively, temperature–measuring devices of equal or better accuracy may be used.

6.5 Oxidation Cell Thermometer, having a range from 80 to 100°C, graduated in 0.1°C, total length - 250 mm, stem diameter - 6.0 to 7.0 mm, calibrated for 76-mm immersion. Temperature measuring devices such as liquid-in-glass thermometers, thermocouples, or platinum resistance thermometers that provide equivalent or better accuracy and precision that cover the temperature range, may be used.

6.6 Wire Coiling Mandrel, as shown in Fig. 2.

6.7 Thermometer Bracket, for holding the oxidation cell thermometer, of 18-8 stainless steel, having the dimensions shown in Fig. 3. The thermometer is held in the bracket by two fluoro-elastomer O-rings of approximately 5-mm inside diameter. Alternatively, thin stainless steel wire may be used.

6.8 Abrasive Cloth, silicon carbide, 100-grit with cloth backing.

6.9 Flexible Tubing, poly vinyl chloride approximately 6.4-mm (1/4-in.) inside diameter with a 3/32-in. wall for delivery of oxygen to the oxidation cell.

6.10 Membrane Filters, white, plain, 47 or 90 mm in diameter, pore size 5 µm.

6.11 Filter Holder, 47 or 90 mm, consisting of a borosilicate glass funnel and a funnel base with a coarse grade (40 to 60-µm) fritted-glass filter support or stainless steel screen support such that the filter can be clamped between the ground-glass sealing surfaces of the funnel and its base by means of a metal clamp.

6.12 Weighing Bottle, cylindrical body with ground-glass stopper; approximate inside diameter 45 mm, height of body 65 mm, capacity 60 mL.

6.13 Vacuum Source, to provide pressure reduction to 13.3 ± 0.7 kPa (100 ± 5 mm Hg) absolute pressure.

6.14 Cooling Vessel - A desiccator or other type of tightly covered vessel for cooling the weighing vessels before weighing. The use of a drying agent is not recommended.

6.15 Drying Oven, capable of maintaining a temperature of 105 ± 2°C.

6.16 Forceps, having unserrated tips.

6.17 Syringe, 50-mL Luer-Lok with 12-in. needle.

6.18 Separatory Funnels, with a capacity of 1000 mL.

6.19 Rubber Policeman.

6.20 Pipette Bulb.

6.21 Syringe, glass or plastic, with Luer-Lok locking connector, 10-mL capacity for sampling.

6.22 Syringe Sampling Tube, Grade 304 stainless steel tubing, 2.11 mm (0.083 in.) outside diameter, 1.60 mm (0.063 in.) inside diameter, 559 ± 2 mm (24.0 ± 0.08 in.) long, with one end finished at 90° and the other end fitted with a Luer-Lok female connector.

7. Reagents and Materials
7.1 Purity of Reagents - Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.

7.2 Purity of Water - Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by Type II of Specification D1193.

7.3 Acetone - Reagent grade. (Warning - Health hazard, flammable.)

7.4 Cleaning Reagent, cleaning by a 24-h soak at room temperature in either Nochromix (Warning - Corrosive, health hazard) or in Micro solution.

7.5 n-heptane, Reagent grade. (Warning - Flammable. Harmful if inhaled.)

7.6 Hydrochloric Acid (Warning - Toxic and corrosive.), concentrated [(36 mass % (relative density 1.19)].

7.7 Isopropyl Alcohol - Reagent grade. (Warning - Flammable.)

7.8 Catalyst Wires:
7.8.1 Low-Metalloid Steel Wire, 1.59 mm (0.0625 in.) in diameter (No. 16 Washburn and Moen Gage).

NOTE 3 - Carbon steel wire, soft bright annealed and free from rust of Grade 1008 as described in Specification A510 is satisfactory. Similar wire conforming to BS 1829, is also satisfactory. If these steels are not available, other equivalent steels may be used, provided they are found to be satisfactory in comparative tests using this Test Method D4310.

7.8.2 Electrolytic Copper Wire, 1.63 mm (0.064 in.) in diameter (No. 16 Imperial Standard Wire Gage or No. 14 American Wire Gage), 99.9 % purity, conforming to Specification B1. Soft copper wire of an equivalent grade may also be used.

NOTE 4 - Alternatively, suitably prepared catalyst coils may be purchased from a supplier.

7.9 Detergent, water-soluble.

7.10 Oxygen - (Warning - Oxygen vigorously accelerates combustion) 99.5 % minimum purity, with pressure regulation adequate to maintain a constant flow of gas through the apparatus. The use of a two-stage pressure regulator on tank oxygen is recommended.

8. Sampling
8.1 Samples for this test can come from tanks, drums, small containers, or even operating equipment. Therefore, use the applicable apparatus and techniques described in Practice D4057.

8.2 For one single determination the minimum required sample size is 300 mL.