Abstract: The present invention provides a process for distillation of styrenes which can be stably operated without loss of energy saving effect, by leading a part or all of low boiling point component vapor from the top to a compressor to use as a heat source for a reboiler and returning the low boiling point components condensed in the reboiler or a mixture of the condensate and a part of the uncondensed vapor to a recycling line of a distillation column.

Abstract: Yarn is continuously supplied to a measuring system with an applied twist of at least 100 turns per meter. A beam having a continuous spectrum from the visible region to the near-infrared region is impinged upon the yarn and measurements are taken on the beams reflected from the yarn. The refected beams are divided into two parts. The characteristics of the near-infrared region are applied to one part, and luminosity characteristics are applied to the other. The ratio of intensity of the former to that of the latter is determined. This ratio corresponds to the uniformity of physical characteristics in the direction of the length of the yarn.