Ill 41 6. Appendix 1. Thermodynamic functions for copper (in calories) 7. Appendix 2. Thermodynamic functions for silver (in calories). 8. Appendix 3. Thermodynamic functions for gold (in calories) V

The hpat ca paci ty of bcryllium aluminate (c hrysobcryl) , BcO' AI 20 3,. ';'a~ ciPtr> rmillC'd from 16 to 380 OK a nd t he t1wrmod y na mi c properti es calculated from 0 to 38() h. .

The normal boiling point and triple point temperatures and the triple point pressure of neon were found to be 27.096 f 0.W K and 24.553 f 0.001 K, and 43332 f 13 N/ma [325.02 f 0.10 mm Hg (0 "C)], respectively. (The temperatures are in tem of the NBS-1955 provisional temperature scale. The figures after the symbol indicate estimated uncertainties.) The triple point pressure is in accord with the more recent values, but the normal boiling point and triple point temperatures deviate significantly from those of previous investigators.

Heat capacities of Ta2H have been determined over a range of temperature extending from 12° to 555°K. Three very sharp A points were observed, at 306, 332, and 333.5°K, suggesting that Ta 2 H exists in four formS-#1 below 306°K, #2 between 306 and 332, #3 at about 333, and a above about 334°K. The heat capacity data for Ta2H are used together with similar data obtained earlier for elemental tantalum and the entropy of formation of Ta2H, evaluated from vapor pressure work by Kofstad, Wallace, and Hyviinen, to compute the residual entropy of #1-Ta2H. This is found to be -0.39±0.30 cal-I deg-I mole-I. The data also are used to estimate configurational entropies of the #2 and #3 forms. These are 0.70 and 3.3 cal-I deg-I mole-I, respectively. The corresponding quantity for the a form is 4.9.The A points are attributed to rearrangements of the hydrogens in the 12-fold more abundant tetrahedral sites. At low temperatures the solute hydrogen atoms are presumed to populate the sites in an orderly fashion. With increasing temperature the ordered arrangement is altered and finally, in the a phase, destroyed. It is inferred from entropy calculations, however, that local order, probably pairing, persists in the a form even to 555°K, the highest temperature studied.Consideration is given to the possibility that the upper two A points, which nearly coincide, should really be one, the splitting being due to concentration gradients or strains. Differential thermal analysis of samples containing from 27.5 to 44.0 atomic % hydrogen suggests that the splitting is a true property of Ta2H. but the results are not completely conclusive.

The heat ca pacity of fl·lithium hexaAuoroaluminate, Li"ALF<; , was de termin e d from 15 to 380 K and the thermodynamic properties calculated from the results. The entropy at 298.15 K was found to be 187.88± 0.38 J/K . mol (44.904± 0.090 callK . mol).