F. E. Poindexter
Jul 1, 1926
Citations
0
Influential Citations
5
Citations
Journal
Physical Review
Abstract
The vapor pressure of solid sodium and potassium amalgams.\char22{}A Buckley ionization gauge was used to measure the vapor pressure of eight sodium amalgams ranging in concentration from 1: 1 to 15: 1 mol ratio of Hg to Na and of 3 potassium amalgams whose concentrations were 5: 1, 10: 1 and 21: 1, Hg: K. The vapor pressure of each amalgam was measured at a number of temperatures which were determined by means of a platinum resistance thermometer. The pressures measured varied from approximately ${10}^{\ensuremath{-}8}$ mm to ${10}^{\ensuremath{-}3}$ mm over a maximum temperature range of from -56\ifmmode^\circ\else\textdegree\fi{} to 90\ifmmode^\circ\else\textdegree\fi{}C. The $\mathrm{log} p$ vs $\frac{1}{T}$ graphs for the different amalgams were found to be approximately straight lines. The difference between the free energy calculated by R. H. Gerke and the internal energy change as calculated in this work shows that the $logp$ vs $\frac{1}{T}$ graphs can be expected to be straight within the experimental error. The heats of reaction were calculated by means of the Van't Hoff reaction isochore, the pressures at different temperatures for these calculations being taken from the $logp$ vs $\frac{1}{T}$ graphs. These heats of reaction for the sodium amalgams varied from 15,000 cal. in the case of the amalgams rich in Hg to 14,000 cal. for the 2: 1 amalgam. This small heat difference over such a wide range of concentrations indicates that most of the heat of reaction between Na and Hg is liberated in the formation of the initial compounds. The heats of reaction for the potassium amalgams were calculated to be 25,500 cal.