4. Significance and Use
4.1 In most of their uses, insulating oils are continually in contact with metals that are subject to corrosion. The presence of corrosive sulfur compounds will result in deterioration of these metals. The extent of deterioration is dependent upon the quantity and type of corrosive agent and time and temperature factors. Detection of these undesirable impurities, even though not in terms of quantitative values, is a means for recognizing the hazard involved.
5. Apparatus
5.1 Bath - A hot-air oven or oil bath provided with suitable means of heating to, and controlling at 140 or 150 mor or less 2°C. A circulating hot-air oven is preferred.
5.2 Flasks - Narrow-mouth, 250-mL, ground-glass stoppered flasks, of chemically resistant glass, capable of holding 270 to 280 mL when filled completely to the stopper. Flasks of such capacity are required in order to allow sufficient space for xpansion of the oil.
5.3 Bottles4 - Heavy walled, 250 mL, bottles of chemically resistant glass constructed with necks to receive a PTFE threaded plug equipped with a fluoro-elastomer o-ring. Bottles of such capacity and design are required in order to allow sufficient space for expansion of the oil and eliminate intrusion from atmospheric gases.
5.4 Copper Foil, 99.9+ % pure, 0.127 to 0.254 mm (0.005 to 0.010 in.) in thickness.
5.5 Polishing Material, consisting of 240-grit silicon carbide paper or cloth, and also 230-mesh silicon carbide grains and pharmaceutical absorbent cotton.
NOTE 1 - It should be noted that 240-grit silicon carbide paper and 230-mesh silicon carbide grains have particle sizes of about the same size (63 µm). In the United States, abrasive papers are classified in accordance with ANSI B74.10. Abrasive powders are classified by ASTM mesh size.
6. Reagents
6.1 Acetone, cp.
6.2 Nitrogen Gas - Commercial cylinders of nitrogen gas are satisfactory for this purpose.
