Physiology. — "(hi tlic spontaneous transforination to <i coUoidal 

 state of solutions of odorous substances by exposure to ultra- 

 violet light." By Prof. H. Zwaahdkmakkk and Dr. F. IIookwind. 



(Clommiinicaled in the meeting of Apiil 26, 1918). 



Tlie literature contains a number of records concerning the sponta- 

 neous transformation to a colloidal state of substances whose 

 molecules contain a noticeably large number of atoms (Blitz') 

 colouring matters) or which are of a corjsiderable molecular weight. 

 (J. Traube^) alkaloids). As one of us had noted the spontaneous 

 transformation of eugenol in glycerin, when these substances are 

 rapidly mixed up, and had been able to establish at the same 

 time several details, wo i-esolved to investigate more systematically 

 the transformation of solutions of odoi'ous substances in water, 

 glycerin, and paraffin. After being rapidly mixed up, the solutions 

 were allowed to stand for weeks and subsequently examined upon 

 Tyndall's effect and observed ultramicroscopically '). 



It appeared that the following solutions yield a strong Tyndall- 

 etTect. 



In this table the odorous substances have been arranged according 

 to their degree of transformation. In a number of cases the obliquely 



') Blitz, Album .1. v. Bemmelen, 1910, p. 110 (boundary value between 45 

 and 55 atoms) 



2) J. Traube, Int. Ztscli. f. Physik. Cliem. Biol. Bd. 1, p. 35, 1914 (boundary 

 value between 208 - 275 molecular weight). 



3) The examination upon Tyndall's eiïccl was performed in the light-cone of a 

 small electric arc-lamp, while watching the complete extinction of the obliquely 



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