858 



TABLE IV. 



The two series of experiments of table III were started at the 

 same moment, the tirst was investigated after three and the latter 

 after six days; when the converted quantity of substance is proportional 

 to the quantity of light and no secondary hindrances occur, the 

 proportion of the quantities of pinacojie at each of the numbers 

 1:1', 2:2' etc. must be the same; these ratios have been inserted 

 in the last column of the second series. 



We notice that this ratio is indeed almost constant except in the 

 case of amyl alcohol, where a hindrance in the form of an increasing 

 yellow coloration is distinctly observed. 



InflMence of the ketone. 



The tubes were filled with solutions of one gram of ketone in 

 50 cc. of absolute ethyl alcohol. Two series were exposed simulta- 

 neously to the action of the light ; the first was investigated after 

 three, the second after six days. Some pinacones remain very long 

 in supersaturated solution, hence the alcohol was always distilled 

 off and the residue shaken with 80 7o alcohol so as to remove all 

 unconverted ketone 



The subjoined table V gives the results obtained and the ratios of 

 the velocities with those of the benzopinacone formation as unit. 



Table VI gives a similar double series; most of the ketones 

 investigated here were not attacked. 



Table VII gives a survey of the results obtained in amyl alcohol 

 as solvent and as reducing agent. 



1®^ The velocity of the pinacone formation, according to this 

 survey, is greatly dependent on the nature and on the position of the 

 substituent. As regards the natui'e, there is only one group (the 

 methyl group on the two para-positions (N". 7)) that appears to 

 accelerate the reduction velocity somewhat, for the rest the substitution 

 causes a decrease in x-elocity. 



This decrease is strongest when the substituting group is a phenyl 



