Researches in colour vision and the trichromatic theory / by Sir William de W. Abney.
- William de Wiveleslie Abney
- Date:
- 1913
Licence: Public Domain Mark
Credit: Researches in colour vision and the trichromatic theory / by Sir William de W. Abney. Source: Wellcome Collection.
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![we place a fiat cell containing a solution of hyposulphite of soda (1 of salt to 10 of water), the disc still remains uncoloured, but if we add a small portion of dilute hydrochloric acid (1 part of acid and 10 of water) to the contents of the cell, the hyposulphite immediately begins to decompose, and very fine particles of sulphur are pro¬ duced in suspension. The image on the screen begins to get yellow, and gradually becomes orange, and finally red, the various stages through which the image passes indicating the diminishing intensity of the colours pro¬ duced by the shorter wavedengths. This can also be exemplified very beautifully by throwing on a screen a longish spectrum of the light of the crater of the arc by means of the lens L1 (Fig. 15), and placing the cell with fresh hyposulphite solution in front of the slit. The colour of the light, which is analysed, can be shown by the patch of reflected light. When the acid solution is added with much stirring, the first effect on the spectrum will be a dimming of the violet, then a further dimming of the same colour, and also of the blue. After a while the green will, with the colours just named, begin to fade. The yellow will next follow, and finally only the red will be light visible. An ocular demonstra¬ tion of the loss of colour is very convincing. The colour of the fine particles does not matter. The particles are so fine that the light is not transmitted through them (to any appreciable extent at all events), and whether it be small particles of sulphur or of any other material, such as smoke, the phenomena detailed above will be observed when a beam of light is passed through them.] The following table, which has been published,1 gives the calculated values of sunlight colours after passage through different atmospheres. 1 “ Colour Measurement and Mixture,” S.P.C.K., and Papers Nos. 8, 9.](https://iiif.wellcomecollection.org/image/b31350574_0076.jp2/full/800%2C/0/default.jpg)
