GB450576A - - Google Patents

Abstract

450,576. Photometric apparatus. BOLTON, E. R., and WILLIAMS, K. A., 6, Milner Street, Chelsea, London. April 26, 1935, No. 12586. [Class 97 (i)] In apparatus for measuring the colour of transparent or opaque substances by a photo-electrical measuring device, the infra red or other undesired rays transmitted by the filter are prevented from impinging on the light-sensitive element. For transparent liquids, light from a lamp 2 is condensed by a reflector 3 and lens 4 into a beam which passes through an adjustable stop 5 into a cell 6 fitted with transparent ends 6a and containing a liquid such as a solution of copper sulphate to absorb infra-red rays. The light then passes through a colour filter 7 into a tray 10 movable on rails 1i and containing two adjacent cells 9, in one of which is a standard liquid and in the other the liquid under examination, each liquid being brought alternately into the beam by sliding tray 10 on the rails. The light finally impinges on a photo-electric cell 11 connected to a galvanometer 12, the reading of which is taken for each liquid alternately, thus allowing the absorption of the examined liquid to be compared with that of the standard. The process is repeated with different colour filters 7 and the spectral absorption of the liquid determined. The scale of the galvanometer may be calibrated to read directly the percentage absorption of light by the liquid, the reading of the standard liquid being first brought to a predetermined value by means of stop 5. For opaque substances the amount of light reflected by the substance may be compared with that reflected by a standard surface such as one of magnesium oxide.