Electrical conductivity of refractories

In the general study of the electrical conductivity of refractories, being conducted by the Department of the Interior at the Columbus, Ohio, experiment station of the Bureau of Mines, tests have been completed ore Maryland, Indian and Italian talcs from 500 deg. cent., to and including 1000 deg. cent. These talcs at thepresent time are being used for the manufacture of electrical insulators and cores for electrical heating appliances. Since 1000 deg. cent, represents the maximum temperature at which these talcs are burned and used, tests were not carried to a higher temperature. Preliminary tests have been made on diaspore and magnesite.