634 Prof. E. C. C. Baly on 



is necessary to open up the closed force field by some means. 

 This may be done by solution in a solvent possessing free 

 force lines or residual affinity, when the closed field of the 

 solute is interpenetrated by the force lines of the solvent, and 

 becomes unlocked and capable of reacting with another 

 substance also in solution in the same solvent. In previous 

 papers* it has been pointed out how this conception is 

 capable of giving an explanation of the phenomenon of 

 stereoisomerism and catalysis. 



The fact that more than one absorption band is given by 

 one and the same substance in different solvents gives at once 

 a reasonable explanation of phosphorescence and fluorescence. 

 The various absorption bands exhibited by the same substance 

 represent various free periods of vibration possessed by the 

 same substance. If now a substance in alcoholic solution 

 exhibits an absorption band and if it is absorbing light of 

 this frequency, it is reasonable to expect that some of the 

 vibrations corresponding to greater stages in the opening up 

 of the closed force field are brought into playj. 



If X : be the wave-length of the absorption band in alcohol 

 when a substance has its force fields opened to a definite 

 stage, and X 2 , \ 3 , &c. be the wave-lengths of light absorbed 

 when it is opened up to greater stages by solution in other 

 solvents, then if the substance in alcoholic solution is ab- 

 sorbing light of wave-length Xi> it is reasonable to expect 

 that some of the more opened up phases will be called into 

 play. In other words, the substance will fluoresce with 

 emission of light of wave-length X 2 , X 3 , &c. The wave- 

 length of the light absorbed by a substance when opened up 

 to a greater stage by solution in a suitable solvent should 

 therefore be the same as the fluorescent light emitted in 

 alcoholic solution when it is only opened up to a lower 

 stage. This has actually been found to be the case, for the 

 fluorescent light emitted by a number of compounds in 

 alcoholic solution is the same as that absorbed by them when 

 in solution in sulphuric acid. Similarly the wave-length of 

 the fluorescent light emitted by the alcoholic solutions of the 

 amino aldehydes and ketones is the same as that absorbed 

 by them in the presence of traces of hydrogen chloride %. 



It follows from this that the fluorescent spectrum of a 

 compound will give a measure of a wave-length of the 

 absorption band of that substance when opened up to a 

 greater stage. 



* Baty, Zeit. Elektrochem. xvii. p. 211 (1911) ; Phys. Zeit. xiv. p. 893 

 (1913). 



t Baly and Krulla, Trans. Chem. Soc. ci. p. 1469 (1912). 

 \ Baly and Krulla, he. cit. 



