September 27, 1912] 



SCIENCE 



393 



group of the terpenes and of the camphors 

 undergo when exposed to light, especially 

 through hydrolytie processes. So far, in- 

 deed, our experiments have taught us that 

 light can spoil rather than improve es- 

 sences. The cyeloketones, for instance, are 

 hydrolyzed and give the corresponding 

 fatty acids; the cycloesanone gives ca- 

 pronic acid and menthone gives decylic 

 acid. 



CO 

 /\ 



CH, CH, 



I I ■ -I- H,0=CH3 . CH, . CBL . CH, . CH, . COOH. 



CH, CH, 



\V 



CH, 



In photochemistry, however, one reac- 

 tion does not exclude the other; the reac- 

 tions may be reversed as some recent ex- 

 periments with ultraviolet rays demon- 

 strate; for the ultraviolet rays sometimes 

 reverse reactions caused by less refrangible 

 radiations. It is important to find suitable 

 sensitizers and catalyzers. We can see 

 what the future has in store for us from 

 such reactions as the photolysis of the 

 ketones, which often accompanies the 

 hydrolysis, and by means of which we pre- 

 pare isocitronellal, for instance from men- 

 thone. 



CH3 

 I 



CH3 



CH3— C— CO . CH3 -> CHs— C -I- CHO . CH3 , 



I I 



CH3 CHs 



is remarkable because it demonstrates what 

 violent decompositions light may cause. 

 It may be an enemy, but just on account of 

 that it is necessary to be familiar with the 

 weapons of the adversaries in order to be 

 able to conquer them and to avail ourselves 

 of their strength. 



I do not believe, however, that the indus- 

 tries should wait any longer before taking 

 advantage of the chemical effects produced 

 by light. The polymerizations, the isomeric 

 changes, the reductions and oxidations with 

 organic and inorganic substances, and the 

 autoxidations which light causes so easily 

 should already find profitable applications 

 in some industries if researches were carried 

 out carefully with this in mind. The ac- 

 tion of light on nitric and nitrosilieic com- 

 pounds, as we know it from experience, is 

 one that ought to be utilized profitably. 

 Our own transformation of orthonitroben- 

 zoic aldehyde into nitrosobenzoic acid has 

 recently been studied by various chemists, 

 and has been made use of by Pfeiffer, 

 who prepared a nitrophenylisatogen from 

 chlorodinitrostilbene. This reminds us of 



CH3 CH3 

 \/ 

 CH 



CH 



/\ 



CH, CO 



I I 



CH, CH, 



\/ 



CH 



I 



CH3 



CH: 



CH; 



3\ 



>CH— CH=CH— CH,— CH— CH,— CHO, 



or the transformation of camphor into an 

 unsaturated cycloketone, etc. The analog- 

 ous breaking down of pinacoline into 

 butylene and acetic aldehyde, 



the not less known transformation of benzy- 

 lidene orthonitroacetophenone into indigo 

 by Engler and Dorant and makes us fore- 

 see a new field in the photochemical pro- 



