STANDARDS FOR A PRACTICAL SCALE OF PD IN HEAVY WATER

The glass electrode has been found to respond to deuterium ion in heavy water solutions as well as to hydrogen ion in ordinary water. Furthermore, the glass-calomel pH assembly is useful for practical measurements of pD in heavy water. Several standard reference solutions for pD are needed, however, as the response of individual glass electrodes is not constant over the entire useful pD range. A suitable phosphate solution (pD 7.428 at 25 °C) composed of KD2PO4 and Na2DP04 (each 0.025 molal) was established in earlier work. This reference has now been supplemented by two other useful buffer solutions, namely 0.05m KD2 citrate (pD 4.293 at 25 °C) and a mixture of NaDCOs and Na2CO3 (each 0.025 molal) which has a pD of 10.736 at 25 °C. Values have been assigned at 10 temperatures from 5 to 50 °C. The conventional pD scale fixed by these three standards has been shown to have a satisfactory internal consistency. © 1969, American Chemical Society. All rights reserved.