160 THE CARBOHYDRATES 



water give rise to hydrogen peroxide and formaldehyde ; the 

 former is acted upon by an enzyme so that oxygen is given 

 off; the latter by the action of the protoplasm is polymerized 

 into carbohydrate. If the formaldehyde be not used up rapidly 

 it poisons the enzyme, so that the peroxide of hydrogen is not 

 decomposed, and will thus destroy the chlorophyll. They also 

 found that the photolysis of carbon diox : de may take place in 

 vitro, provided one of the products be removed. 



From further experiments they conclude that the formation 

 of formaldehyde from carbonic acid in the presence of chloro- 

 phyll is independent of vital or of enzymic activity ; the pro- 

 ducts of such decomposition are formaldehyde and peroxide 

 of hydrogen, formic acid being an intermediate product. Also 

 they find that it is possible to reconstruct the photosynthetic 

 process outside the green plant as far as the production of 

 formaldehyde and oxygen, by the aid of a suitable catalysing 

 enzyme, and as far as the production of oxygen and starch by 

 the aid of non-chlorophyllous protoplasm together with the 

 enzyme. 



They, in addition, repeated Bach's experiments referred to 

 above and found that formic acid is a product of the photolysis 

 of carbonic acid in the presence of an inorganic salt of uranium ; 

 and that formaldehyde is probably formed as a transitory 

 intermediate product. 



In the following year, 1907, Fenton * found that in the 

 presence of magnesium which substance, there is reason to 

 suppose, is the active principle of chlorophyll formaldehyde 

 may be obtained from an aqueous solution of carbon dioxide, 

 more especially if weak bases be present. 



Usher and Priestly also found that an aqueous solution of 

 carbon dioxide could be decomposed by the a and /3 rays from 

 radium emanation. The action of -oooi c.c. of radium emana- 

 tion on 200 c.c. of water saturated with carbon dioxide resulted 

 in four weeks in the production of hydrogen peroxide and 

 formaldehyde. Most of the latter was in a polymerized state, 

 but the solution contained no sugar. 



Similar results were obtained by the action, on solutions of 

 carbon dioxide, of the ultra violet rays given off by a quartz 



* Fenton : " J. Chem. Soc., Lond.," 1907, 91, 687. 



