86 PROCESSES OUTSIDE THE LIVING CELL CHAP. 4 



In 1931, Baly reported two new methods for obtaining catalytically active prepara- 

 tions: electrolytic precipitation of basic nickel or cobalt carbonates, and deposition of 

 thorium oxide-" promoted " ferric or chromic oxide on alumina-coated kieselguhr 

 (diatomaceous earth). However, Bell (1931) was unable to repeat these experiments, 

 and the same disappointment was later experienced by Baly himself. In 1937, Baly 

 announced that "two methods of preparing active catalysts have been now standard- 

 ized." In 1939, he described the results obtained with these new catalysts; the whole 

 development, from the "early investigations" to the "final achievement of photo- 

 synthesis of carbohydrates," was reviewed in Baly's monograph, Photosijnthesis, in 1940. 



The two new methods of preparation of the sensitizers were: (a) the deposition of 

 nickel oxide or cobalt oxide on kieselguhr; and (6) the precipitation of (unsupported) 

 nickel oxide by the addition of potassium bicarbonate to a solution of nickel nitrate, 

 and heating of the precipitate in vacuo. The first method, although more compMcated, 

 had the advantage that the supported oxide layers did not dissolve in carbon dioxide- 

 saturated water. 



In the investigation of Baly, Pepper and Vernon (1939), the surface potentials 

 (f potentials) of the oxide-coated kieselguhr powders were measured by cataphoresis, 

 and it was concluded that the coating consisted of three monomolecular layers. One 

 molecule of thorium oxide was incorporated into the surface layer for each 24 molecules 

 of nickel oxide. 



In the preparation of unsupported oxide, attention was directed to the avoidance 

 of the adsorption of alkah, which, according to Baly, is the main source of trouble 

 with oxide catalysts. The unsupported catalysts, too, were prepared with one molecule 

 of Th02 as "promoter" for each 24 molecules of NiO. 



The successes obtained with the new preparations did not go beyond 

 those achieved in 1927. Ten to 20 g. of the catalyst were suspended 

 in 1.5 liters of air-free, carbon dioxide-saturated water, at 30° C, and 

 illuminated for two hours by two 250-watt lamps. The irradiated 

 liquid, separated by filtration, gave a positive Molisch test upon satura- 

 tion with sulfur dioxide. If the solution was left standing for two 

 hours, or heated to 60°, the test became negative; this was taken as proof 

 that the first product of artificial photosynthesis was unstable. Upon 

 evaporation of the liquid, a whitish precipitate was obtained, which was 

 shown by charring to contain some organic matter; but 30 mg. of this 

 matter, collected from several irradiations, gave only traces of carbon 

 dioxide and water in a microcombustion. This was attributed by Baly 

 to the content of the precipitate in silica and was not considered by him 

 as a decisive argument against its predominantly organic nature. The 

 precipitate was taken up in a little water, and treated for two hours with 

 takadiastase at 37°. The product, tested with Fehling's solution, gave 

 7-8 rag. of cuprous oxide. This was taken as a proof that the white 

 precipitate contained "a kind of starch," which the diastase had con- 

 verted into a reducing sugar. The yield of cuprous oxide could not be 

 increased by prolonged irradiation; this was attributed by Baly to a 

 poisoning of the catalysts by the products of photosynthesis. 



This is what Baly called the "final achievement" of photosynthesis 

 in vitro! It contained no proof of oxygen liberation; no proof of carbon 



