On a new type of electric furnace, with a redetermination of the melting-point of platinum

Abstract

An investigation is now in progress in the thermometric department of the National Physical Laboratory, having for its object the design of an electrical method of measuring temperatures from 1200° C. upwards in some such way as temperatures below this value may now be determined by an appropriate thermocouple or resistance thermometer. It is, of course, common knowledge that metals such as platinum and alloys of the platinum group are unable for prolonged periods to withstand, without alteration of their structure and properties, the effects of temperatures above about 1200° C., particularly if in presence of even small quantities of certain gases, such as are very difficult to ensure shall be completely absent, especially at the higher ranges. This is the case with nearly all methods of heating, whether electrical or otherwise. The brilliant researches of Moissan on the stability of all kinds of substances at very high temperatures, and the recent work of Nernst culminating in the invention of his well-known lamp, in which the light giving filament is formed of a complex mixture of oxides of rare earths, directed the attention of the author to this class of bodies. From a study of their behaviour he has been able to work out a method of attaining by very simple means very high temperatures, which may be controlled with great ease. A preliminary account of this new type of electric furnace, with some results of investigations undertaken with it, forms the subject matter of the present paper.