The a va ilable data on the thermodynamic properties of the elem ents lithium, sodium, p otassi um, rubidium, a nd cesium have been analyzed, a nd selected values of these properties are presented in tabular form . The tables inclu de valu es of the free-energy function,
(F°-HO)/ T ; heat-content function, (H O-H a) / T; entropy, S o; heat content, (l-I°-H a) ;heat capacity, C~; heat of formation, !!.l--Ij" ; free energy of format ion, !!.Fj"; and logarithm of tlle equilibrium constant of formation, log Kf , for the solid, the liquid, and the monatomic a nd diatomic gases as a function of temperature from 0° K to high temperatures.
. IntroductionAs part of a general program on the collection, analysis, and compila tion of data on the ch emical thermodynamic proper ties of chemical substances [1 , 2),3 a survey has bee n m ade of aU of the available data relatin g to the thermodynamic properties of t he alkali m etals, li thium, odium, potassium, rubidium, and cesium. There is co nsid erable in terest in the usc of these m etals in chemical synt he e , as well as in their use as heat-transfer media. A large amount of new data has become available sin ce tbe early summaries of Gordon [3] a nd K elley [4,5]; it is believed that a complete s ummary of t he data on t hese clements presented in a convenient tabular form will be very useful to enginccrs, physicists, a nd chemists engaged in pr oblems involvin g t hese substances. This s urvey will also indicate gaps a nd weaknesses in t he prese nt state of our knowledge with r espect to these s ubstanc es and indicate areas r eq uirin g addi tional r esearch.
Units and Standard StatesThe calorie used in t hese calculations is the thermochemical calorie, defined by the relation : 1 cal = 4.1840 abs j. The other cons tan ts are those given by Wagman et al. [6]. The ice point, 0° C , is taken as 273.16° K [71. The chemical atomic weights [8] used are: Li, 6.940; Na, 22.99 1; K , 39.10; Rb , 85.48; Cs, 132.91. For gases t he standard state chosen is the hy pothetical ideal gas at I-atmosphere pressure. For solids and liquids t he standard state is taken as tb e substance under I-atmosphere pressure (o r sat ura ted vapor pressure, if this is greater). As is custom ary, nuclear spin a nd isotopic mixing contributions to th e free-energy function and entropy are omitted; all values are for t he naturally occurring isotopic mixt ure. The ymbols used for thermodynamic quantities arc those used previously [1,2].
83
. Calculation of the Thermodynamic Functions
Monatomic GasesThe translational contributions to the thermodynamic fun ctions of the monatomic gases Li, N a, K , Rb , and Os were calculated by use of t be equaLions given by Wagman et al. [6] (corrected for t he new defini tion of the thermochemical caloric). The additional contributions due to electronic excitation are easily obLained in terms of t he par tition function , Q, a nd tbe derived fun ctions Q' a nd Q" Q' = ~i gi (~dkT) e-E .lk T These conlributions were evalu ated by direct summation. Th e energy level...
