Methyl chloride (CHP) has a boiling point of ?10.6°F (?23.3°C). It also has heat of vaporization at boiling point (at l atm) of 177.8 Btu/lb. It is a good refrigerant. However, because it will burn under some conditions some cities will not allow it to be used. It is easy to liquefy and has a comparatively high latent heat value. It does not corrode metal when in its dry state.
However, in the presence of moisture it damages the compressor. A sticky black sludge is formed when excess moisture combines with the chemical. Methyl chloride mixes well with oil. It will operate on a positive pressure as low as ?10°F (?23°C). The amount of vapor needed to cause discomfort in a person is in proportion to the following numbers:
Carbon dioxide 100
Methyl chloride 70
Ammonia 2
Sulfur dioxide 1
That means methyl chloride is 35 times safer than ammonia and 70 times safer than sulfur dioxide.
Methyl chloride is hard to detect with the nose or eyes. It does not produce irritating effects. Therefore, some manufacturers add a 1 percent amount of acrolein as a colorless liquid with a pungent odor as a warning agent. It is produced by destructive distillation of fats.
