Heavy Water and Water of Crystallisation

Abstract

The statement made by Prof. Erlenmeyer and Mr. Gartner in Nature of September 1, that, by crystallising sodium sulphate from solutions containing a few per cent of heavy water, the latter is divided practically equally between the water of crystallisation and solution, is in harmony with experiments I carried out some months ago. To ascertain if heavy water normally present in ordinary water could be concentrated by crystallisation, several litres of warm saturated solution of sodium sulphate were cooled. The crystals that separated were heated and the refractive index of the expelled water was determined with the Pulfrich refracto-meter as this was thought to afford a sensitive method of observing any change in the composition of small quantities of water. The dehydrated salt was added to the original solution and a fraction again crystallised out. This process was repeated many times until the original solution was reduced to small bulk. No change in the refractive index could be detected, however, between the initial and final fractions from either crystals or solution. It does not appear possible, therefore, to concentrate heavy water in this manner.