the EDITOR'S column L.T. Hallett, Editor
T
H E THERMODYNAMIC
PROPERTIES
of solutions of deuterium chlo ride in heavy water have been de termined recently at the N a t i o n a l B u r e a u of S t a n d a r d s I n s t i t u t e for M a t e r i a l s Research ["Thermody namics of Solutions of D e u t e r i u m Chloride in H e a v y W a t e r from 5° to 50° C , " R o b e r t Gary, Roger G. Bates, and R. A. Robinson, J. Phys. Chem., 68, 1186 (1964)]. The study is the first in a series aimed at developing a scale to measure deuterium ion activity in solutions of heavy water. Increased use of heavy water has renewed interest in the properties of acids a n d bases in this solvent and has underscored the need for a " p D " scale. I n establishing such a scale, precise measurements of the conventional deuterium ion activ ity, by the electromotive force method, in a variety of useful buffer solutions are necessary. These buffer solutions must cover a wide- range of deuterium ion a c tivity. Before the ion activity of buffer solutions can be calculated, however, the standard e.m.f. of the cell. P t ; D 2 ( g . , 1 a t m . ) , DC1 in D 2 0 , AgCl; Ag, designated Cell I, m u s t be accurately measured. Cell I consists of a solution of deuterium chloride in hea\'y water, a silver-silver chloride electrode, and a platinum electrode over which deuterium gas is bubbled. The physical configuration of the cell is based on the design of cells used to measure hydrogen ion activity in solutions of hydrogen chloride in ordinary water. However, t h e present cell is more a d a p t a b l e for use with different solvents a n d in corporates a number of new fea tures to increase its accuracy and precision. T h e e.m.f. of Cell I was compared with t h a t of t h e " h y d r o gen" cell in which the deuterium,
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