A system of physical chemistry - Index of

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A system of physical chemistry - Index of

MOLECULAR HEATS OF POLYATOMIC SOLIDS 79

its present formulation. It is not improbable that considerable modifications

may eventually be introduced. It represents, however, a

partially successful attempt to solve the problem of the heat capacity of

polyatomic substances.

We shall conclude this chapter by quoting some numerical data

obtained by Eucken {Ber. Deutsch. phys. Ges., 18, 4 (1916)) in connection

with the heats of fusion and vaporisation of certain condensed

gases at low temperatures :—

Molecular Heat

Substance. of Fusion in

Calories.

Argon 267-9

Nitrogen .......... i68'7

Oxygen 105-5

Carbon monoxide ........ 224-1

Nitrogen was found to exist in two solid forms, the temperature of

transition being 35*5° abs. and the molecular heat of transformation

53*8 cals. Oxygen exhibits three solid forms ; transition temperatures,

#3 "5° and 42*5° abs., the corresponding molecular heats of transformation

being 17*5 and 167*4 cals. respectively. Carbon monoxide exists

in two solid forms ; transition temperature, 60*4° abs., molecular heat

of transformation, i44"i cals.

Molecular Heat

Substance. of Vaporisation

in Calories.

Hydrogen 2^9

Nitrogen 1363

Oxygen 1599

Argon . 1501

Carbon monoxide . . . . . .1414

Eucken {loc. has likewise measured the cit.) specific heats of solid

and liquid argon, nitrogen, oxygen, and carbon monoxide the ; specific

heats of solid carbon dioxide and of liquid hydrogen, and likewise the

specific heat of highly compressed gaseous helium.

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