GE CTR 80 User Manual

8.1.10.3 Mineral OilMineral oil or paraffin oil is often used at moderate temperatures above therange of water. Mineral oil is relatively inexpensive. At lower temperaturesmineral oil is quite viscous and control may be poor. At higher temperaturesvapor emission becomes significant. The vapors may be dangerous and use of afume hood is highly recommended. As with most oils mineral oil will expandas temperature increases so be careful not to fill the bath too full that it over-flows when heated. The viscosity and thermal characteristics of mineral oil ispoorer than water so temperature stability will not be as good. Mineral oil hasvery low electrical conductivity. Use caution with mineral oil since it is flam-mable and may also cause serious injury if inhaled or ingested.8.1.10.4 Silicone Oil (Dow Corning 200.05, 200.10, 200.20)Silicone oils are available which offer a much wider operating temperaturerange than mineral oil. Like most oils, silicone oils have temperature controlcharacteristics which are somewhat poorer than water. The viscosity changessignificantly with temperature and thermal expansion also occurs. These oilshave very high electrical resistivity. Silicone oils are fairly safe and non-toxic.Silicone oils are fairly expensive.8.1.10.5 Halocarbon 0.8Halocarbon 0.8 is a low temperature fluid with a wide temperaturerange. It may be used as low as –90 to –100°C before viscosity be-comes too great. It may be used as high as 70°C before evaporation be-comes excessive. Halocarbon does not absorb water and will thereforeform ice at temperatures below 0°C. Ice crystals turn the fluid into aslush which effectively increases the viscosity and reduces temperaturestability. Pumping systems may be rendered ineffective due to ice block-age. The ice (water) can be removed occasionally by heating the fluid upto 100°C for brief periods of time. Use halocarbon under a fume hood athigher temperatures to remove vapors. Toxicity is low but caution is al-ways recommended. Halocarbon has excellent electrical resistivity. Thisfluid is fairly expensive.8.1.11 Fluid Characteristics TableTable 2 on page 31 provides help in selecting a heat exchange fluid media foryour constant temperature bath. This table provides a numerical representationof most of the physical qualities important in making a selection. The list is notall inclusive. There may be other useful fluids not shown in this listing.The table includes information on a variety of fluids which are often used asheat transfer fluid in baths. Because of the temperature range some fluids maynot be useful with your bath.308 General Operation