Sulfur as a Standard of Reflectance in the Infrared

The development of an instrumental setup for measuring reflectance of diffusing materials in the infrared region from 2 to 15 μ and a standard for reflectance measurements in that range are described. Magnesium oxide, which generally is used as a standard for reflectance measurements in the visible range, has a very low reflectance beyond 2.7 μ. Flowers of sulfur, containing an estimated amount of approximately 30% mu form of sulfur, or other sulfurs which contain more than 30% mu sulfur, such as vaporized and quenched high-polymer sulfur, have been studied as a reference material in the determination of the infrared reflectance of diffusely reflecting surfaces; and the calculations have been shown for its application in reflectance measurements. The selection of the mu sulfur compounds has been discussed, based on comparison with other sulfur forms which lack the required characteristics for a suitable reference standard in infrared reflectance work.