FUNCTIONS DISCHARGED BY THE CHLORINE AND HYDROGEN RESPECTIVELY. 3 



(c.) To the chlorine an equal volume of hydrogen was now added, the vessel being, 

 consequently, full of the united mixture. The force of the ray was again measured, 

 and found to be represented by 19 seconds. 



(d.~) Lastly, the first (a) of these preceding measures was determined again, with a 

 view of ascertaining whether the intensity of the lamp had declined, or the apparatus 

 remained in its first condition. It gave again 12 seconds. 



321. Let us group these four results together, representing thus the intensity of the 

 beam by the time it requires to produce a given effect : 



A beam through the glass vessel 12 seconds. 



Chlorine 25-5 " 



Chlorine and hydrogen 19 " 



Atmospheric air ....... 12 " 



We therefore gather from this, that the addition of hydrogen to chlorine, far from in- 

 creasing its absorptive power, actually diminishes it. That in the case before us, 

 where to a given volume of chlorine an equal volume of hydrogen has been added, the 

 absorptive power is diminished to one half. 



322. We farther see, that the action of the beam is expended primarily on the chlo- 

 rine, giving to it a disposition to go into union with hydrogen, and that the functions 

 discharged by the chlorine and hydrogen respectively are wholly different. 



323. The chemical forces of the ray are easily deduced from the foregoing meas- 

 ures, in which the times are given, for it is obvious that they are inversely proportional 

 to those times. 



324. The second and third experiments (b~) and (c) may, without sensible errcr, be 

 taken as representing the activity of the ray in vacuo, for, as will be seen, upon prin- 

 ciples hereafter given, a ray which has passed through atmospheric air has not under- 

 gone any absorptive action, and therefore does not differ from one which has passed 

 a vacuum. Consequently, those measures give us the effect of chlorine, and of chlo- 

 rine and hydrogen, compared with a vacuum. The absorptive action of the glasses is 

 common to all the experiments, and may therefore be left out of the final estimate. 

 The difference of the resulting numbers in b and c, from the probable numbers 25-5 

 and 18-7, may be accounted for from the disturbing causes which are encountered, such 

 as the constant solution of chlorine by the salt water, &c. 



325. When, therefore, a ray of light falls upon this changeable compound, chlorine 

 and hydrogen, the primary action takes place upon the chlorine, which becomes titho- 

 nized, or has a disposition given to it to go into union with the hydrogen; the latter 

 gas appears to be passive, so far as the ray is concerned. In the mean time, the ray 

 itself becomes changed, undergoing absorption action, and being detithonized. 



