The photosynthesis of naturally occurring compounds.—II. The photosynthesis of carbohydrates from carbonic acid by means of visible light

Abstract
When H2CO3, adsorbed on the surface of Ni or Co carbonate suspended in water, is exposed to visible light, photosynthesis of organic compounds takes place. One at least of the products of this photosynthesis is a carbohydrate which reduces Benedict''s solution, gives the Molisch and Rub-ner reactions, and forms a solid osazone. The photo-synthesized material contains 1 or more complex substances which are hydrolyzed by acid to give substances which reduce Benedict''s solution. For equal areas of the suspension exposed to the light the yield of organic products is greater than that obtained with white powders in the light of the quartz Hg lamp. The % of carbohydrates in the products photosynthesized with a colored surface in white light is greater than when white powders are used in ultra-violet light. If ammonium bicarbonate solution containing Ni or Co carbonate in suspension is exposed to visible light complex N compounds are synthesized. The shift in the exciting wave-length from the ultra-violet characteristic of CO2 in solution to the visible region characteristic of natural photosynthesis has been achieved in the laboratory. The photosynthesis by means of visible light has the advantage in that the photochemical decomposition of the products is avoided. Further, the special difficulties connected with the use of quartz apparatus with ultra-violet light are removed. The O set free during the photosynthesis tends to poison the surface. When moist Ni and Co carbonates are exposed to visible light in an atmosphere of CO2, a surface film of Ni2O3 and CO2O3, respectively, is formed. The surface when poisoned by O slowly recovers itself under water, with the result that increased yields of the carbohydrates are obtained with unit quantity of light when the intensity of illumination is decreased. When the surface has become completely poisoned the photosynthesis ceases, and then with intense illumination the carbohydrates previously formed are photochemically composed. Since rigid tests established the freedom of the CO2 and all the materials from all organic impurity, and since over 200 control experiments, periodically carried out, invariably gave entirely negative results, it would seem impossible that the photosynthesized carbohydrates arise from organic impurity.

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