US EPA

1237931 

Technical Report 

Determination Of Fumigants. XIII. Determination Of Chlorohydrocarbons By Thermal Decomposition 

Winteringham, FPW 

1942 

NIOSH/00136361 

61 

190-192 

A procedure for the determination of chlorohydrocarbons using thermal decomposition was developed. The airstream containing the sample was drawn into the thermal decomposition apparatus by means of a rotary vacuum pump. The inlet contained cotton wool as a dust filter. The sample passed through three towers packed respectively with caustic soda, calcium-chloride, and activated charcoal. The air was then directed into an aeration flask, either directly or via a bubbler containing distilled water. Dry or moist air then entered the thermal decomposition tube. This was a transparent silica tube, kept at about 900 degrees-C by an electric furnace. The air and decomposition products were bubbled through two sintered glass plate bubblers charged with 2 normal (N) sodium-hydroxide. The chloride (16887006) present was determined by titrating with 0.1N silver-nitrate, using a potassium-chromate indicator. Before titration, any hypochlorites present were reduced with sodium-sulfite. The precision of the method was tested using milligram quantities of chloroform (67663), carbon-tetrachloride (56235), pentachloroethane (76017), trichloroethylene (79016), tetrachloroethylene (127184), and methylallyl-chloride (563473). Recoveries ranged from 95 to 105 percent. The method was applicable to samples drawn in evacuated flasks, using castor-oil as a solvent. The sampling head could be replaced by the aeration head necessary for the thermal decomposition apparatus without loss of sample. The author concludes that this method can be useful for the determination of chlorohydrocarbons in samples of fumigated material. 

DCN-124307; Trace analysis; Analytical methods; Analytical chemistry; Physical properties; Chemical properties; Testing equipment; Laboratory testing; Heat exposure; Chemical analysis