The gassing properties of aromatic hydrocarbons

Last year at this conference we discussed various methods for measuring the gassing properties of cable oils under electrical stress and described a modification of the Pirelli test designed for rapid and convenient operation. In using this apparatus on various natural and synthetic hydrocarbon oils, we have found a great diversity in gassing behavior, especially with changes in temperature. While the gassing coefficient of some oils is nearly unaffected by changing temperature, that of other oils changes rapidly and may actually reverse its sign. In some cases an increase in temperature will cause a gas-adsorbing oil to become gas-evolving; in other cases the reverse change may take place.In order to understand the behavior of commercial oils, we believe it is necessary first to study the behavior of pure hydrocarbons, both aromatic and aliphatic, and of their binnary mixtures. Only when the behavior of these simple cases is understood, can the behavior of complex mixtures be adequately interpreted. The present paper reports some results obtained in the first part of the above research, namely, measurement of the gassing coefficients of a number of pure aromatic and alkyl aromatic hydrocarbons. These measurements were all made in the modified Pirelli cell using a paper wick as described in our previous paper.