On the specific inductive capacity of a sample of highly purified Selenion

Abstract

For the purpose of the electrical measurements, the selenion, purified as described in R. Threlfall’s paper, was cast into the form of a circular plate about 15 cm. in diameter and 1 cm. thick. To make the casting, the selenion was heated until thoroughly liquid, which occurred at a temperature between 200° and 230° C., then poured into an open zinc mould previously warmed, and allowed to cool at the air temperature. Under the circum­stances the selenion assumed the vitreous form, the fracture being conchoidal and the specific gravity 4·29 at 13°·8 C. When hard, the end surfaces of the plate were carefully ground flat and parallel to each other, the grinding being done with carborundum powder. After the completion of each set of measurements the plate was broken into small pieces to ascertain if the material was homogeneous throughout ; on no occasion were any air bubbles found which could in any way affect the accuracy of the measure­ments. Determinations of the specific inductive capacity of the selenion forming the plate so prepared were made by the absolute electrometer method, with alternating electric forces having a frequency of about 50 per second ; and by a method using electric oscillations with a frequency of 24,000,000 per second. Table I gives the results obtained, the measurements being made with the selenion in the dark.