Connexion between Light and Chemical Energy. 209 



region o£ the phenomena and of proper methods to illustrate 

 this successfully. 



In this communication the author will chiefly give his 

 consideration to the phenomena he dealt with in the above 

 experimental research, leaving the consideration of other 

 regions to be dealt with by subsequent investigations. 



The condition of equilibrium of a homogeneous system (in 

 the dark) is the following : 



dFi = tdr)— pdv-\-fiid »>!...+ fA n d nin^O (Gibbs' equation 12). 



Let us now assume that the above homogeneous system with 

 independent variables (i. e., in which the substances do not 

 act one upon another chemically) is in equilibrium in the dark. 

 Let this system be now exposed to some constant source of 

 light, say to the light emitted by a perfectly black body when 

 it is heated up to the temperature necessary for its beginning 

 to emit light, or to the light from any other source, having 

 the same intensity and the same composition, or to a con- 

 stant source of the aether vibration of electric waves. Let 

 us also assume that the system is always removed from the 

 source of light by the same distance, which may be chosen 

 ad libitum, so that the intensity of the light falling on the 

 system always remains the same. Let us further assume 

 that the layer of the homogeneous system is only taken very 

 thin, or that the absorption of the light by the given system 

 is so small that the intensity of the light falling upon the 

 system in the different planes which are in a vertical position 

 to the propagated rays of light, practically remains the same. 

 When the system with independent variables is exposed to 

 light, in the first instance it always absorbs more or less light, 

 energy. Since no energy can be lost in nature the light ab- 

 sorbed mi^tof necessity transform in the system into some other 

 form of energy. As the light absorbed does not transform into 

 heat (molecular action] alone, even when no visible chemical 

 reaction takes place, it must of necessity transform into some 

 form of kinetic energy of the atoms in the molecules as well. 

 From a molecular mechanical point of view this will mean that 

 under the influence of light the amount of work present in the 

 molecules in the form of energy of the atoms will increase. 



Since every system, including those in which light produces 

 no chemical change, continues to absorb light as long as it is 

 exposed to it ; since the absorption-coefficient of a substance 

 is independent of the time of its exposure to the light, and 

 since no energy can be lost m nature, we further arrive at 

 the following conclusion : Either the system is able to stoic 

 an infinite amount of energy coming from any source of light, 

 if it is only infinitely long exposed to it, which is an impossi- 

 Phil. M«i. 8. (5. Vol. 5. No. 2(5. Feb. L903. V 



