Cell Dimensions of Ordinary and Heavy Ice

Abstract

I HAVE recently made accurate determinations of the cell dimensions of crystals of ordinary and heavy ice (D₂O). Single crystals were used. The apparatus consisted of a small Dewar flask mounted on the arcs of a Bernal photogoniometer, and filled with a mixture of acetone and solid carbon dioxide. A holder of copper wire attached to the bottom of the flask contained a capillary tube of Lindemann glass, into which a drop of water was sealed. The crystal was grown by inserting the glass tube into its holder in contact with the cooling mixture; its growth was observed with a polarising microscope, and it was thawed and grown again until a good single crystal was obtained. The direction of fastest growth was the normal to (11&2bar;0), so that this direction generally grew along the axis of the tube. There was a steep temperature gradient in the crystal; at the holder it was very nearly at 78° C., while its top, about 3.3 cm. above this, was at the melting point, and was in contact with a layer of liquid. The spacings could thus be determined at different temperatures.