855 



More accurate experiments were not considered necessary as we 

 did not care for the absoliile value, but only for the order of mag- 

 nitude of the temperature coefticient. 



Adjacent to the jacketed tube was also suspended an ordinary 

 tube to ascertain whether the presence of the jacket had any influence 

 on the pinacone formation. 



The subjoined table II gives a survey of some series of experiments. 



From these results it follows that the method is sufficiently accurate 

 for our purpose, the ketone reduction is indeed a photo-reaction 

 with a small temperature coefficient; this still' falls below the mean 

 stated by PlotiNikow^ ) of 1,17 per 10°. 



TABLE II. Time of exposure 2—3 days. 



NO. 



Contents of inner tube 



temp, 

 interval 



pinacone 



K, 



^-flO 

 AT. 



1st Series 

 1 



2 

 3 



2 gr. (C6H5)2 CO in 25 cc. alcohol \ 25°— 28° 

 without jacket 



with jacket 



75°— 78° 



4- 50° 



0.45 gr. 



0.76 „ 



1.02 „ 



1.06 



2nd Series 

 1 

 2 

 3 



without jacket 25°— 28° 

 with jacket „ 



75°— 78° 



+ 50° 



0.44 gr. 

 0.70 „ 

 0.96 „ 



1.065 



3rd Series 

 1 



2 

 3 



2 gr.(CiC6H4)2CO in 25cc. alcohol 

 without jacket 



with jacket 



25°— 28^ 



75^—78 



50- 



0.27 gr. 



0.35 „ 

 0.55 „ 



1.095 



4th Series 

 1 

 2 

 3 



without jacket 25^-28- 

 with jacket 



75'^- 78° 



+ 50° 



0.24 gr. 

 0.30 „ 

 0.50 „ 



1.10 



JoH. Plotnikow. Photochemische Versuchstechnik. p. 273 (1912), 



