DESIGN, CONSTRUCTION AND TESTING OF A HEAT OF VAPORIZATION CALORIMETER USEFUL IN THE VAPOR PRESSURE RANGE 1 TO 0:01 MM HG AT 25 C
Abstract
A method for the experimental determination of heats of vaporization at 25 C of substances exerting a vapor pressure in the range .01 mm Hg has been developed. A micro-calorimeter was constructed in the form of a Knudsen cell from which the substance was evaporated into high-vacuum. With a charge of about 300 mg of sample usually 5 to 8 consecutive experiments were performed. The vaporization heat was electrically compensated. The even-numbered n-alkanes from octane to hexadecane served as test substances. A further control was obtained by measuring heats of vaporization of n-propyl disulfide and benzenethiol. Heat of sublimation and vaporization values were determined for solid and liquid samples of phenyl diacetamide, and the difference was compared to the experimentally determined heat of fusion. It is believed that, at present, the accuracy of the corrected results is at least 0.1 kcal/mole. At a vapor pressure of .001 mm, the error was found to be as much as 2+3 kcal/mole. It is likely that this discrepancy is due to the existence of a residual pressure close to the evaporation cup of the same order of magnitude as the vapor pressure of the substance. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 21, 1962
- Accession Number
- AD0277721
Entities
People
- Stig Sunner
Organizations
- Lund University