1640 
For d we find the same impossibility : now, the part represented 
by a straight line must pass through 3 of the points Bn EN 
while here on the same surface “@ no intersection in f#vo points 
can occur. 
It is therefore evident that of none of the degeneracies a part can 
pass through one of the base-points P,,..., P,. Through an arbitrary 
point P,' in 2’ no bitangent of #7 passes. All the bitangents are 
therefore lying in (80—n) separate bitangent planes. 
The surface itself must be a cone. 
Chemistry. — “The photo-oxidation of alcohol with the co-operation 
of ketones. Contribution to the knowledge of the photochemical 
phenomena.” Il. By Prof. J. Borsexen and Dr. W. D. Conen. 
(Communicated in the meeting of March 25, 1916), 
At the meeting of 31 Oct. 1914 some particulars were commu- 
nicated by us as to this reaction; since then we have made a closer 
study of the same and a few important results thereof are found in 
the dissertation of one of us’). 
The reaction scheme: 
2 ketone + alcohol = pinakon + aldehyde-(ketone), 
deduced from comparative velocity measurements with increasing 
quantities of aleohol could be confirmed in various ways. 
First of all it was demonstrated that in this reaction the 
aliphatic aleohol was converted quantitatively into aldehyde (ketone, 
respectively) and not into the correlated aliphatic pinacone. 
The acetone obtained in the reaction: 
2 C,H,COC,H, + CH,CHOHCH, = [(C,H,),C(OH)]|, + (CH,),CO 
was thus weighed in the form of the p-nitrophenylhydrazone and 
the cyclohexanone formed in the reaction: 
2 C,H,COC,H, + C,H, OH (cyclohexanol) = [(C,H,),COH], + C,H,,0, 
was determined by the “oxime method”. 
That, in the photo-oxidation of aromatic alcohols, the said reaction 
scheme was also correct was proved as follows: 
If the reaction had taken place according to the equation: 
C,H,COC,H, + C,H,CHOHC,H, = [(C,H,), C(OH)], 
which also would have been in harmony with the unimolecular 
course of the reaction, then when taking the two following mixtures: 
1) Dissertation W, D, Conen, Delft 1915, 
