I. A. The Oxidation Potential of Cerous-Ceric Salts in Aqueous Nitric Acid Solution. B. The Oxidation Potential of Thallous-Thallic Salts in Aqueous Nitric Acid Solution. II. An Attempt to Determine the Electrode Potential and Raman Spectrum of Fluorine. The Entropy of Fluorine. III. A. The Construction of a Low Temperature Vacuum Calorimeter. B. The Heat Capacity of Monofluorotrichloromethane from 60°K to its Boiling Point. Its Heat of Fusion, Heat of Vaporization, Vapor Pressure and Entropy

Citation

Garner, Clifford Symes (1938) I. A. The Oxidation Potential of Cerous-Ceric Salts in Aqueous Nitric Acid Solution. B. The Oxidation Potential of Thallous-Thallic Salts in Aqueous Nitric Acid Solution. II. An Attempt to Determine the Electrode Potential and Raman Spectrum of Fluorine. The Entropy of Fluorine. III. A. The Construction of a Low Temperature Vacuum Calorimeter. B. The Heat Capacity of Monofluorotrichloromethane from 60°K to its Boiling Point. Its Heat of Fusion, Heat of Vaporization, Vapor Pressure and Entropy. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/jzs3-pj92. https://resolver.caltech.edu/CaltechTHESIS:01142025-192537228

Abstract

I. A. Potential measurements made at 25 and 0°C on cells of the type

Pt + H₂(p atm.), HClO₄(c'), {HNO₃(c) + Ce^IV (c₂)/Ce^III (c₁)}, Pt

give the value 1.6093 ± 0.0007 volts for the formal cerous-ceric oxidation potential at 25°C, substantially independent of the nitric acid concentration in the range 0.5 to 2f.

The decrease in free energy, heat content and entropy at 25°C found for the reaction

Ce^IV(1f) + E^-I = Ce^III(1f)

in nitric acid 0.5 to 2f are, respectively, 37,120 cal., 34, 970 cal. and -7.2 cal./deg.

Evidence is discussed for nitrate complex ions of both cerous and ceric ions in nitric acid.

B. Measurements on cells of a similar type involving thallium salts give 1.2302 ± 0.0007 volts for the formal thallous-thallic oxidation potential at 25°C, independent in the range 0.5 to 2f of the concentration of nitric acid.

For the reaction T1^III(1f) + 2E^-I = T1^I(1f)

in nitric acid 0.5 to 2f the decrease in free energy, heat content and entropy at 25°C were found to be 56,800 cal., 30,700 cal. and -87.6 cal./deg., respectively.

II. An attempt to experimentally determine the electrode potential of fluorine met with failure because of non-reproducibility.

No Raman lines due to fluorine could be discovered when plates were exposed up to four hours to the light of a mercury arc scattered by liquid fluorine in a quarts container.

The value 48.6 cal./deg./mole has been calculated for the standard virtual entropy of fluorine from the internuclear distance and Badger's Rule. The calorimetric data of Kanda lead to a value which has been shown to be too low.

III. A. A vacuum calorimeter has been constructed for the determination of heat capacities of condensed gases from 60°K room temperature. Descriptions of it, the manometer, electrical circuits and instruments, and of the establishment of a temperature scale are given.

B. The heat capacity of crystalline CCl₃F has been measured from 60°K to its melting point (162.54 ± 0.05°K), and the heat capacity of the liquid determined from the melting point to the boiling point.

The heat fusion at the melting point has been determined as 1641.8 ± 3.2 cal./mole.

The vapor pressure of the liquid was determined over the pressure range 5 to 72 cm. Hg; the observations can be represented by the equation:

log₁₀ P (int. cm Hg) = -1610.04/T + 8.21671 - 0.0030743 T/

From this equation the normal boiling point is calculated to be 296.88 ± 0.05°K, and the heat of vaporization at the boiling point to be 5905 ± 30 cal./mole after a Berthelot correction of -220 cal./mole is made. The Trouton's constant is then 19.89.

An extrapolation of the heat capacity to the absolute zero gives 71.92 ± 1.5 cal./deg./mole for the standard virtual entropy of the ideal CCl₃F gas. This value is 2.2 cal./deg./mole lower than the "spectroscopic" value.

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