1897-98.] Note on certain Chemical Reactions. 
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Preliminary Note on a Characteristic of Certain 
Chemical Reactions. By Prof. John Gibson, 
Ph.D. 
(Read December 6, 1897.) 
In a paper, communicated to the Society in February 1897, the 
author drew attention to increase in electrical conductivity as a 
characteristic of photo-chemical action. 
This increase in electric conductivity may he explained by 
assuming that light acts either in the direction of increased 
conductivity, or as a disturbing agent on molecular systems having 
an inherent tendency towards rearrangements involving increased 
conductivity. 
It may he that both assumptions are correct. 
Since making this communication the author has been engaged 
in experimental investigation, undertaken in order to elucidate this 
subject further — more particularly in its chemical aspect. 
The behaviour of nitric acid with respect to light appeared 
especially suggestive. Nitric acid on progressive dilution with 
water becomes less and less subject to decomposition by light, until, 
as that dilution which corresponds to maximum conductivity is 
approached, the action of light seems to cease altogether, so that 
nitric acid at all dilutions greater than that corresponding to its 
maximum electrolytic conductivity appears to he unaltered by 
light. It seemed, therefore, desirable to investigate experi- 
mentally the purely chemical behaviour of nitric, hydrochloric, 
and sulphuric acids at different degrees of dilution with water. 
The investigation is now sufficiently far advanced to justify the 
communication to the Society, in this preliminary note, of some 
of the conclusions which have been arrived at. 
It would appear that the chemical behaviour of the acids just 
mentioned depends, in many of their reactions, on whether their 
concentration is above or below that corresponding to their maxi- 
mum electrolytic conductivity. 
VOL. XXII. 7/2/98 
C 
