REVERSIBLE AND IRREVERSIBLE SYSTEMS UNDER INFLUENCE OF LIGHT. 387 
K the constant of equilibrium. This law giving the connection between the 
constant of equilibrium, absolute temperature, and the intensity of light (given first 
by the author in the ‘ Zeitschr. fur physik. Chemie,’ 1902, vol. 42, pp. 319, 333, 
‘ Phil. Mag.,’ 1903, (6), pp. 211, 214), is thus amply verified on several systems in this 
research. 
(d) On the Connection between the Velocity of Chemical Reaction produced by the 
Action of Light, the Intensity of Light and Absolute Temperature. 
From the above equation (a) it follows :— 
(a) When both opposite reactions go on under the action of light only : 
RT log 8 Ki = C'T or RT log e K x = C"I + (K) and RT log e K 2 = C '"I 
or RT log e K 2 = C"T + (K). 
(b) If only one of the reactions goes on under the action of light, while the other 
opposite one goes on also in the dark (and its velocity is not influenced essentially 
by light) 
RT log, K x = C'T+RT logg K n . 
At a constant temperature 
logg Kj = C /V I + K 1V . 
The above gives the true law for the connection between the velocity constant 
of chemical reactions produced by light, the intensity of light and the absolute 
temperature (after the induction period has passed). 
(e) The Velocity of Molecular or Physical Reactions between different parts of the 
Heterogeneous System produced by and going on only under the Action of Light 
evidently folloivs the Law found by the Author for these Reactions in the Dark. 
The equations found experimentally by the author for the induction and deduction 
periods ^ — c (7r' 0 — n) (tt— 7t 0 + K) and — ^ = — c' (v 0 —i r) (it— -n-'o + K') (see ‘ Proc. 
(IT (XT 
Roy. Soc.,’ vol. 74, 1904, p. 369) give the speed of transformation of a substance 
(Ag, AgBr, Cu, &c.) from its state of equilibrium with its ions in solution in the dark 
to its state of equilibrium with its ions in light and vice versa. They correspond 
both in form and content to the general equation C ~ = c (t 0 —t) (t — £ 0u + K), or ^ 
(XT C IT 
= c (2 + K) (t 0 — t), which, as I established experimentally, is giving the speed of all 
molecular or physical reactions between different parts of the heterogeneous system 
in the dark. 
A full account of my investigations was given in the ‘ Report of the British Associa- 
3 D 2 
