A physical study of the Welsbach Mantle

The investigation here described, in so far as it deals with the radiating characteristics of the incandescent mantle, constitutes chiefly an extension of the work of Rubens on the thoria-ceria mixtures, to a large family of such combinations. It exhibits the Welsbach mantle of commerce simply as one of a group of possible combinations of radiating materials, behaving according to the same general laws, but remarkable among them for the degree to which the characteristics of selective radiation are exhibited.A more detailed study has been made than any heretofore on the behavior under various conditions of the absorption bands to which the enhanced visible radiation of the more efficient mantles are due. While no explanation has been found for the occurrence of the visible absorption bands of ceria and other materials—a question to be solved only by an intimate knowledge of the structure of matter—the information learned as to the conditions under which they appear and disappear has made possible a rather complete explanation of some long-standing enigmas, notably that of the different behavior of the mantle in flame and cathode-discharge heating.Another line of investigation has here been taken up apparently for the first time in any detail; namely, that of the energy relations holding with flame heating of radiating materials. As a result of the study it has been possible to fix with some definiteness the possible attainable efficiencies of gas-light production by present methods. These, while low, are still many times any now reached.