856 



That the temperature coefficient for or^A^^chlorobenzophenone is 

 really somewhat higher than for benzophenone seems to ns rather 

 probable, but this can only be ascertained by more delicate measu- 

 rements ^). 



The independence of the concentration and the very small tempe- 

 rature coefficient now enables us to continue followiiif»- tliis very 

 sfmple method in the quantitative investigation as to the influence 

 of the ketone to be reduced as well as of the reducing alcohol. 



Influence of the alcohol. 



Tlie alcohols, as described above, were carefully dried o\er calcium 

 and, after distillation, poured at once into the tubes containing two 

 grams of ketone. These were then sealed and exposed to the light. 



These tubes were suspended at such a distance that they could 

 not interfere with each other. 



The subjoined table gives two series of experiments, the first series 

 was exposed for three and the second one for six days : particularly 

 during the first days it was sunny spring weather. 



What strikes us here in the first place is the agreement in the 

 action of the alcohols 2 — B; the secondary propyl alcohol gets 

 oxidised somewhat more i-apidly. the amyl cilcohol a little more 

 slowly. In the latter case a strong yellow coloration sets in. 



Very much smaller is the velocity of the pinacone formation in 

 the case of methyl and allyl alcohol; as no interfering yellow 

 coloration occurred here and as the conditions were moreo\er quite 

 equal, this ditferent behaviour must be attributed to the particular 

 position these alcohols occupy. 



Although Ave cannot yet enter here into an explanation of the 

 process, it is obvious that the reduction of benzophenone will proceed 

 all the more readily when in the conversion of alcohol ijito aldehyde 

 (or ketone) more energy is set free. 



The absolute extent of this energy is unknown to us, but still 

 some thermic data point to the existence of a parallelism in the 



1) The remarkably greater leduclion velocity in the jacketed as compared with 

 that in an ordinary tube, must be attributed to the larger quantity of light which, 

 owing to refraction in the jacket filled with water, falls on the inner tube. In fact 

 nothing could be noticed of this inner tube when the tube was entirely filled ; it 

 looked as if the alcoholic solution has the width of the outer tube. In harmony 

 with this observation, it appears that the ratios of the velocities in the four series 

 namely 76:45, 70:44, 35:27 and 30:24 do not greatly diverge and are about 

 equal to the proportions of the sections of the outer and inner tube 24 ; 16. 

 (Compare Luther and Weigert 1. c. p. 391). 



