The determination of small amounts of water by entrainment distillation

Abstract

A simple apparatus and procedure are described for the determination by entrainment distillation of 0·01-ml amounts of water. Errors inherent in many previous designs arising from the use of a reflux condenser are avoided by condensing the distillate vapour as it flows downwards. A determination, including the time for conditioning the entraining liquid in the apparatus, can be performed in less than 30 minutes. Xylene is recommended as the entraining liquid.

In a series of determinations to assess the recovery of known amounts of water, a small constant loss was observed together with a further loss proportional to the amount of water added. After correcting for the constant loss, mean recoveries of 98 to 100 per cent. were obtained. The coefficients of variation (single determination) were about 10 per cent. and 1 to 2 per cent. at the 0·01 and 0·2-ml levels, respectively.