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HEAT AND FREE ENERGY OF VAPORIZATION EQUATIONS 59
and of Maier, while for the liquid he is in approximate agreement with
Maier, who covered only a short temperature interval. The equa-
tions that follow are based on Stirnemann's work. The specific heat
of the gas is taken as 34 calories per mole of Fe2C16. The variation in I
for the solid is 0.16 unit and for the liquid 0.05 unit. The latter figure
applies only to vapor pressures below 2 atmospheres. The data of
Stirnemann go up to over 9 atmospheres, but the figures above 2 atmos-
pheres have not been considered because of the effects of gas imper-
fection, which are readily apparent in the 1-function plot.
Solid- Gas (Fe2C16)
C (g) = 34,
C,(s) = 40.8+ 26.4 X 10-3T,
AC=- - 6.8- 26.4X 10-3T,
AH= 41,400 - 6.8 T- 13.2X 10-3T2,
AFo 41,400+ 15.7 Tlog T+13.2X 10-3T2- 122.17 T,
AH298.1= 38,200; AF298.1 = 17,735.
Liquid-- Gas (Fe2C16)
C (g) =34,
C (1) = 64,
AC,= -30,
AH-29,800-30 T,
AFO - 29,800+69.1 T log T- 241.90 T,
B. P.= 5920; AH592- 12,040; AS592 = 20.3,
AH298.1 20,860; AFo298.1= 8,659.
From these equations it follows that the heat of fusion at the
melting point, 5770, is 20,590 calories per gram formula weight.
Carbonyl.-Iron pentacarbonyl, Fe(CO)5, was studied in the
liquid state by Trautz and Badstiibner (413) (320-3780). If ACp
is neglected, their extensive set of data shows a variation in I of
0.12 unit, two determinations being discarded.
Liquid-- Gas (Fe(CO)5)
AH= 9,000,
AF= 9,000- 23.83 T,
B. P.= 3780; AS378= 23.8
AF0298s.= 1,896.
KRYPTON
Element.-The vapor pressure of krypton was studied by Allen
and Moore (3) (114-1210), Peters and Weil (283) (81-1220), and
Ramsay and Travers (296) (84-2910). The most extensive data
for the solid are those of Peters and Weil, with which the other
results are in fair agreement. The liquid range is not considered
here, since the results of Allen and Moore and of Peters and Weil
cover only a short temperature interval and those of Ramsay and
Travers are very erratic. The melting point is 116.50, and the
boiling point of the liquid is 120.20, according to Allen and Moore.
Solid- Gas (Kr)
AH= 2,540,
AFo= 2,540-21.03 T.
LEAD
Element.-Several investigators have studied the vapor pressure
of liquid lead-Egerton (96) (600-1,200'), Greenwood (131, 132,
133) (1,593-2,373), Harteck (144) (1,353-1,4770), Ingold (175)
(1,195-1,611), Leitgebel (23) (2,0130), Rodebush and Dixon (309,
310) (1,391-1,5970), Ruff and Bergdahl (316) (1,548-1,8280), and
Von Wartenberg (425, 427) (1,081-1,9030). The results show con-