September 27, 1912] 



SCIENCE 



391 



been obtained by D. Berthelot. With con- 

 venient modifications could not this now 

 actually be done on the tropical high- 

 lands? Yet the true solution consists in 

 utilizing the radiations that pass through 

 the entire atmosphere and reach the sur- 

 face of the earth in large amounts. That 

 a way of accomplishing this exists is proved 

 by the plants themselves. By using suit- 

 able catalyzers, it should be possible to 

 transform the mixture of water and carbon 

 dioxide into oxygen and methane, or to 

 cause other endo-energetic processes. The 

 desert regions of the tropics, where the con- 

 ditions of the soil and of the climate make 

 it impossible to grow any ordinary crops, 

 would be made to utilize the solar energy 

 which they receive in so large a measure 

 all the year, that the energy derived from 

 them would be equal to that of billions of 

 tons of coal. 



Besides this process, which would give 

 new value to the waste products of com- 

 bustion, several others are known, which 

 are caused by ultraviolet radiations and 

 which might eventually take place under 

 the influence of ordinary radiations, pro- 

 vided suitable sensitizers were discovered. 

 The synthesis of ozone, of sulphur trioxide, 

 of ammonia, of the oxides of nitrogen, as 

 well as many other syntheses, might be- 

 come the object of industrial photochem- 

 ical processes. 



It is conceivable that we might make 

 photoelectrical batteries or batteries based 

 on photochemical processes, as, for in- 

 stance, in the experiments of C. Winther. 



Passing to the field of organic chemistry, 

 the reactions caused by light are so many 

 that it should not be difficult to find some 

 which are of practical value. The action 

 of light is especially favorable to processes 

 of reciprocal oxidation and reduction 

 which give rise to or are associated with 

 phenomena of condensation. Since the 



common condensation is that of the aldolic 

 type there is much hope for the future, the 

 aldolic condensation being the funda- 

 mental reaction of organic synthesis. 

 Some experiments recently made by my 

 friend Silber and by myself may serve 

 here as an illustration. The simplest case 

 is that of the action of light on a mixture 

 of acetone and methyl alcohol in which 



CH. 



CH, 



CO + OH30H=COH— CHjOH 

 I I 



CH, CHa 



isobutylene glycol is produced. But this 

 condensation which may be considered as 

 a simultaneous process of oxidation and 

 reduction, is accompanied by the reduction 

 of the ketone to isopropyl alcohol and by 

 the oxidation of the methyl alcohol to for- 

 maldehyde, which latter, however, does not 

 remain as a product which can be isolated, 

 because it reacts with the remaining 

 methyl alcohol and is transformed into 

 ethylene glycol: 



CO -I- 2CH3OH -^ CHOH -I- 



CH, 



CH, 



Applying the same photochemical reac- 

 tion to the mixture of acetone and ethyl 

 alcohol we have analogous products: tri- 

 methylethylene glycol ; and along with this 

 isopropyl alcohol and dimethylethylene 

 glycol : 



CHOH 

 I I 



COH— CH.OH and CHOH. 

 I I I 



With acetone and isopropyl alcohol, as 

 could be expected, there is formed only 

 pinacone : 



