The emissivity of metals and oxides. II. Measurements with the micropyrometer

Abstract

As indicated in a communication describing the micropyrome- ter,^this instrument may be used conveniently for the approxi- mate determination of the monochromatic emissivities of metals, oxides, and other substances in microscopic quantities at high temperatures. This method has the further advantages of sim- plicity and rapidity of operation and also permits the taking of observations on rare elements, alloys, and compounds which are available only in minute quantities. It is possible, for example, under favorable conditions to measure with an accuracy of about I per cent the emissivity of a substance having a mass of o.oi mg, an area of 0.25 mm^, and thickness of 0.005 ^^-The method lends itself readily to the determination of a temperature coef- ficient of emissivity and to the detection of a variation of emissivity with change of state, as at the melting point. The temperature range of the micropyrometer for these purposes is from about 700 to 3000C.