258 



TEMPERATURE COEFFICIENT OF /3-RAYS 



fall about two parallel lines, as illustrated in Fig. 1. The line drawn 

 through the points obtained at the higher temperature lies above the 

 other, showing that the velocity of the reaction has been increased 

 by the higher temperature. The velocities (Ki and A'2) at the two 

 temperatures (h and ^2) are inversely proportional to the times re- 

 quired to produce membranes of any given volume. Thus in the ex- 

 periment illustrated in Fig. 1, 40 minutes of exposure were necessary 

 to produce a membrane of 10 hundred thousand cubic microns at 0°C. 

 At 24° C. this membrane volume is represented by a point on the curve 

 corresponding to an exposure of 27 minutes. We may then write 



— = — where /i = and h = 24. 

 Ki 27 



equation^ 



Substituting these values in the 



lU 



we obtain 1.18 as the value of Qio, the temperature coefhcient for a 

 change of 10°C. Table I gives a number of determinations of Qw 

 made in this way. 



TABLE I. 



The source of radiation used in this investigation was radium ema- 

 nation enclosed in slender, thin-walled glass tubes. The walls of 

 these tubes were sufficiently thick to absorb all the a-radiation. 

 We expect to show in a future publication that the effect of the 

 7-rays from such a tube is negligible compared to that of the /3-rays 

 in producing the reaction. The coefhcient which we have determined 

 is therefore that of the action of the jS-rays.* 



' We are indebted to Dr. William Duane and to the Director of the Cancer 

 Commission of Harvard University for placing a supply of radium emanation at 

 our disposal. 



