AND STATICS UNDER THE INFLUENCE OF LIGHT. 
3 9? 
K ; and K" are integration constants. Assuming now that the system consists of 
several substances, as given in (a), and that the law of Dalton holds good for the 
chemical and for the light-kinetic potentials, then we get from (/3) that 
io£r { a-y ■ (^r/m = sr ikk.' - t - (»»+»i - %) bt 
+ ( ni H,' + njH,' - « 3 H 3 ') log T + (« 3 K 3 " - K" - % K a ")] . . (iv.), 
where —7 5 Dl , Ul are the concentrations of each substance expressed in gram- 
m. 
m, 
v 
molecules, n x , n 2 . . . the numbers of grammolecules of each substance taking part in 
the reaction, u< 3 K 3 '— n x K/— n^KJ — constant EA, — (n 3 +%— w 3 ) RT is the work done 
by the system (a) during the transformation in light, (?qH/ -j- njl 2 ' — n 3 H 3 ') log T 
+ (n 3 ^ 3 " - «i K 1 " — is the heat of reaction in light. Thus the connection 
between the logarithm of the constant of chemical equilibrium in homogeneous 
systems in light, the heat of reaction or of transformation of ?q grammolecules 
of Sj plus n 2 grammolecules of S 2 into n ?j grammolecules of S 3 in light, the work done 
during the transformation, and the absolute temperature, follows the same law in light 
as it does in the dark. The effect of light upon a system therefore consists in shifting 
it to a new point of equilibrium. It is further easy to show that at a constant 
volume, since the work — (?? 2 + n x — n 3 ) B/T = 0, and r/t' can be put —. C,T, where 
C, is the specific heat at a constant volume, T the absolute temperature, an equation 
is arrived at, which after differentiation gives 
lQ g(v 
~k 1° 
P* 
fpf' 
i 
& \ V’ 
n 2 
A + BT 
RT 2 
,(v.), where A and B are constants (equation of Uan’t Hoff and Kooy), 
’m 2 '\ n ‘ lfm 2 ' \ r ‘ 3 
which at a constant temperature gives [prj ’ j~ constant (vi.), i.e., the 
law of mass action holds good for chemical equilibrium in light, as found experimentally. 
Decomposing this equation for homogeneous systems in the usual manner into two, 
giving the two opposite velocities of reaction, which at equilibrium become equal, 
we get 
/ _7 -. ' / f ... / , v,. / /\ -.j. / .7 \ // I ' \ 
. . (vii.), 
/ dec V 
( dT ) ~ C \v 
/ / " l l 
m/\ n ' /md\ n * 
yra„dUU" = c"(^r. 
i.e ., the velocity of chemical reaction in light must also follow the laws of mass 
action, as found experimentally. 
In conclusion, I should like to express my thanks to the Managers of the Davy- 
Faraday Laboratory of the Royal Institution for having allowed me to make use of 
the splendid arrangements of the Laboratory, and especially to Dr. Ludwig Mond, 
who by his kind assistance has enabled me to undertake and carry out the above 
research, and who by his valuable advice on many occasions has very essentially 
contributed to the success of the same. 
