I. Preliminary Studies in the Application of a Ballistic Piston to Investigation of Chemical Reaction in the Nitrogen-Oxygen System. II. Isobaric Heat Capacities at Bubble Point of Pseudocumene and of n-Heptane

Citation

Helfrey, Paul Francis (1957) I. Preliminary Studies in the Application of a Ballistic Piston to Investigation of Chemical Reaction in the Nitrogen-Oxygen System. II. Isobaric Heat Capacities at Bubble Point of Pseudocumene and of n-Heptane. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/0TX5-XZ31. https://resolver.caltech.edu/CaltechETD:etd-07212004-115113

Abstract

An apparatus, in which gaseous samples may be subjected to rapid compression, is described. This "ballistic piston" offers a mechanically simple method of producing for a short time a very high temperature and pressure in a sample under study. The results of preliminary studies on the nitrogen-oxygen system are presented. Appreciable yields of nitrogen dioxide, up to 3.3 mol per cent of the gas remaining after compression, were obtained. The conditions investigated involved calculated maximum temperatures as high as 13,000[degrees] R and maximum pressures up to 30,000 psi. The maximum temperature and pressure achieved in each run were calculated on the basis of fairly simple assumptions. An increase in the yield of NO2 with increasing maximum temperature and with increasing maximum pressure was noted. Coefficients for a second order rate equation were tested by comparing predicted yields based on the coefficients with the observed yields. In the temperature range above 3500[degrees] R rate coefficients not more than one-tenth as great as those obtained by extrapolation of existing data are indicated. The rate coefficients obtained are subject to much uncertainty because of the many simplifying assumptions made in treating the data. The results are discussed in the light of the limitations imposed by the assumptions. As part of a long-term project for measurement of the heat capacities of hydrocarbons, the isobaric heat capacity at bubble point of 1,2,4,-trimethylbenzene (pseudocumene) was determined in the range 70-210[degrees] R. Using the same equipment, the same property was determined for n-heptane, a widely accepted standard for calorimetric work. The results are reported in a manuscript which includes results obtained by a later investigator on the project for 1,3,5-trimethyl-benzene.

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