31 



means a mixed color, the yellow component of which can be in- 

 tensified by freezing the solution of the alkaloid in the presence 

 of 10"^ M potassium iodide. In lysergic acid (10-* M) the blue 

 fluorescent light emission of the watery solution assumes a pur- 

 plish color on freezing and can be shown to contain, at the side of 

 fluorescence, a strong long-lived phosphorescence in the presence 

 of 1% glucose. 



Such changes are not limited to fluorescent substances. Isopenta- 

 quine, for instance, emits under the UV lamp a strong orange 

 light if frozen in dry ice. This light emission is composed of a yel- 

 low fluorescence (which can be greatly increased by 10% glucose) 

 and a red phosphorescence which can be seen in the fast phos- 

 phoroscope and can be somewhat increased by 10"^ M glutathione. 

 A frozen blue tetrazolium sends out orange-green light, composed 

 of a green fluorescence and a red phosphorescence visible in the 

 fast phosphoroscope. Chlorophyll behaved like other fluorescent 

 dyes: on freezing its watery solution completely lost its brilliant 

 red fluorescence.^ 



In all instances the light emission, observed on cooling, had a 

 longer wavelength than the fluorescence of the unfrozen solutions. 

 Phosphorescence, as a rule, has a longer wavelength than the cor- 

 responding fluorescence. Spectra were known to have a tendenq^ 

 to shift towards a longer wavelength on intense cooling, but the 

 fact that water so completely and dramatically changes the situa- 

 tion was, to my knowledge, not known or appreciated. 



These experiments are so simple that they ought to be repeated 

 by everybody interested in this field. They should be repeated even 

 in the classroom. They demand no paraphernalia, except an UV 

 lamp and some dry ice. Doing an experiment is different from 

 reading about it. These experiments make the impression of a 

 new, colorful world opening up unexpectedly and promising a 

 deeper insight into the mechanisms of life and their interaction 

 with their matrix, water. 



^ "Chlorophyll, water soluble" of Fisher Scientific Co., New York was 

 used. 



