New Form of Saccharimeter

Abstract

THE saccharimeter, as constructed for many years, differs from the polarimeter in that it contains a system of dextro- and Iævo-rotatory quartz wedges between the polarizer and analyser, the adjustment of the wedges replacing the rotation of the analyser. Monochromatic light must be used for polarimetrie readings, but with the quartz wedge saccharimeter bichromate-filtered white light can be used since the rotation dispersions of quartz and carbohydrate solutions are almost the same. Until recently it has not been practicable to obtain monochromatic light of sufficient intensity and constancy for use under ordinary laboratory conditions, and the saccharimeter with white light illumination has almost universally been used for sugar analysis. A very satisfactory source of monochromatic light is now obtainable, however, in the form of an electric sodium lamp, and its introduction has led Messrs. Bellingham and Stanley, Ltd., to construct a saccharimeter, without the quartz wedge device, for use with sodium light ; the instrument is identical in principle with the polarimeter and differs from the latter only in being provided with a sugar scale, reading from –30 to +110 International sugar degrees. This scale, like the angular degree scale of the polarimeter made by the same firm, is etched on a glass circle and, unlike the ordinary saccharimeter scale, requires no magnification ; the Vernier attachment, also, is etched on a glass plate. The elimination of the quartz wedge system has several advantages. It obviates any error due to want of optical homogeneity of the quartz, it renders unnecessary the exact adjustment of the temperature of the apparatus to that of the observation tube and the reading is taken, not by reflected, but by transmitted light.