. SELIG HECHT 371 



IV. 



Equation (3) states that 



E = kt log / (3) 



For purposes of experimental verification, and for convenience in 

 presenting the data, it will be desirable to consider equation (3) as 

 follows. The reaction time {r) is equal to the sum of the time occu- 

 pied by the sensitization period {t) and the latent period {p) . There- 

 fore 



r = t-\- p 



and 



t = r-p (4) 



Substituting this value of t in equation (3) we get 



E = k(r-p) log I 



and from it that 



r = K-^+p (5) 

 log/ 



1 



where K = y It is at once apparent that equation (5) is in the 

 form of the equation of a straight line 



y = ax -{- b 



where y = r,or the reaction time; a = K;x = =, which is equiv- 

 alent to the reciprocal of the logarithm of the intensity, since E, the 

 photochemical effect, is constant; and b = p, the latent period. 



It follows from this consideration that if equation (3) is true, a 

 curve, representing as ordinates the reaction time (r) and as abscissae 



the reciprocal of the logarithm of the corresponding intensity ( , )' 



should be a straight line which crosses the y axis at p units above (0,0). 

 I have drawn the data of Fig. 1 in this way, and the result is given 

 in Fig. 2. The fact that the curve in Fig. 2 is a straight line is direct 

 proof of the experimental validity of equation (3) and of its deriva- 

 tive, equation (5). The data of the other six series of experiments 

 show precisely the same thing. For further emphasis Fig. 3 is pre- 

 sented, which gives the data of two other experiments. The three 



