THE VAPOR-PRESSURE OF LINDANE (GAMMA-1,2,3,4,5,6-HEXACHLOROCYCLOHEXANE) - A COMPARISON OF KNUDSEN EFFUSION MEASUREMENTS WITH DATA FROM OTHER TECHNIQUES

The vapor pressure of pesticides is an important parameter for predict ing the distribution of these substances in the environment. Using the Knudsen effusion technique and highly purified samples of lindane (ga mma-1,2,3,4,5,6-hexachlorocyclohexane), a thorough reinvestigation of its vapor pressure has been undertaken. The results obtained are compa red with previously published values, some of which show considerable scatter, especially at temperatures of natural field conditions. We co nsider our data to be sufficiently accurate to be used as reference va lues, e.g. for calibrating other less direct techniques of vapor press ure measurement. On account of our measurements in the range (292 to 3 26) K we recommend for lindane the vapor pressure equation In p/Pa = ( 34.53 +/- 0.21) - (11754 +/- 72)(T/K)(-1).