Survey of alkanone reactivity based on time required for 50% oximation

Abstract

ture. However, we think that such a correction would not substantially modify our values of excess entropy. This view is supported by comparison with the Ga-Bi system (9) which is analogous to the Ga-Pb system in many aspects. In fact, excess entropies are positive in bismuthrich alloys (-0.07 e.u. at 90 at. % Bi) and negative at intermediate compositions (-0.2 e.u. at 30 at. YO Bi). This is not surprising, because lead and bismuth are neighbors in the sixth period of the Periodic Table and have similar properties as shown in Table I I I . A s one can see, the difference in electronegativity for Ga-Bi alloys is greater than or at least equal to that for Ga-Pb alloys. Taking into account the errors which affect the electronegativity values, one could attribute the differences of excess entropies between Ga-Bi and Ga-Pb alloys to electronic peculiarities. This seems supported by the maximum mixing enthalpy of Ga-Pb alloys which is larger than that of Ga-Bi alloys (920 and 504 cal/g-atom, respectively). At present, we cannot regard the excess entropies of Ga-Pb alloys as more reliable than those of Predel and Stein for our assumption on Newman-Kopp law validity. Further calorimetric measurements of mixing enthalpies at 1143K should be carried out to get entropy values from direct experimental data.