Abstract
Phillips' rubber scale is often used for calculation of Rf-values in paper chromatography. One may, however, feel insecure as its reliability depends upon the uniformity of elongation of the rubber plate. We have therefore devised a scale made of celluloid or transparent plastic plate in the form of right-angled triangle with graduated lines drawn parallel to its base. The scale is so placed on the paper that the apex of the triangle is located at the original line of the paper and its base line at the end line of solvent. The graduated line passing through the center of each spot indicates its Rf-value. This scale can show exact values and is advantageous as it can be used in the dark room if substance is fluorescent.
