August 25, 1922] 



SCIENCE 



231 



tween those which are not homologous. They 

 show, furthermore, that the correlation between 

 the winter periods of the first and second year 

 is the lowest of any of the four correlations 

 between the productions of homologous periods. 

 The difference between the winter-winter corre- 

 lation and the spring-spring correlation is not 

 large, but the differences between the winter- 

 winter correlation and the summer-summer and 

 the autumn-autumn eoeffleients are more sub- 

 stantial, the two latter being 2.57 and 6.10 

 times as large as their probable error. 



In so far as this type of evidence is pertinent 

 to the problem, it indicates that in the White 

 Leghorn at least there is no evidence of special 

 factors which distinguish the "winter cycle" 

 from any other period of the year. 



J. Arthur Harris 

 H. R. Lewis 

 Station for Experimental Evolution, 

 Cold Spring Harbor, N. Y. 



THE EFFECT OF X RAYS ON CHEMICAL 

 REACTIONS 



While investigating with Dr. E. Dershem 

 absorption coefficients for X rays, a brass cell 

 with aluminum windows containing cyclo- 

 hexanol was subjected to the X rays and after- 

 wards opened. The contents showed very 

 striking and unexpected consequences due to 

 this exposure. The colorless hexanol had 

 turned to greenish-blue, and later analysis 

 showed that about 0.1 of a gram of copper had 

 gone into solution. 



The intensity of the X rays was so small, 

 coming as a nearly monochromatic beam from 

 a crystal grating, that the amount of chemical 

 action produced was most surprising. The 

 geometry of our apparatus and the power used 

 by the X ray bulb enabled us to calculate the 

 maximum energy which could be involved. 

 Assuming the target and the crystal grating to 

 be 100 per cent, efficient, and taking one hour 

 as the maximum time exposure, the energy 

 received by the cell could not be greater than 

 3 X 10" ergs, or less than 0.1 of a calorie. 



Using the quantum theory, we may calculate 

 from the wave length, approximately 0.2 A, 

 the number of quanta entering the cell. The 



energy per quantum is 1 X 10"' ergs. There- 

 fore the number of quanta received could not 

 be greater than 3 X 10"^^. Since about 0.1 

 gram of copper went into solution each quan- 

 tum must have caused at least 3.3 X 10" atoms 

 of copper to react. 



The small amount of energy involved, and 

 the small number of quanta relative to the 

 number of atoms reacting, indicate that the 

 reaction is an exothermal one. The quantum 

 voltage producing the X rays was approxi- 

 mately 10^ volts. Since each quantum caused 

 3.3 X 10' atoms^ to react, not more than 

 3 X 10"^ volts could be expended on each atom 

 if the reaction were endothermal. This value 

 is only one five-hundredth of the smallest 

 I^nown resonance potential, that for cfesium as 

 determined by Foote, Rognley and Mohler,- 

 being 1.48 volts. 



We therefore must conclude that the X rays 

 produced some sort of trigger action of the 

 type studied by Bodenstein and Taylor" and by 

 Jorissen and Ringer* in their work on the 

 formation of hydrochloric acid from hydrogen 

 and chlorine by means of alpha particles. An 

 excellent discussion of this work will he found 

 in a monograph bj' Lind."' 



Mesitylene showed a behavior similar to that 

 of eyelohexanol, but in this case the color was 

 a yellowish green. This difference in color may 

 be due to concentration effects. 



On account of the large effect produced by 

 relatively small amounts of energy, it seems 

 that the use of X rays may acquire great im- 

 portance in the production of organic com- 

 pounds, especially if substances are produced 

 in this manner which can not be obtained by 

 other means. 



A. R. Olson 

 National Research Fellow in Chemistry 



University of California, 



= Foote, Eognley and Mohler, Fhys. Hcv., 61 

 (1919). 



s (M. Bodenstein) and H. S. Taylor, J. Am. 

 Chem. Soc, 37: 24 (1915). 



1 Jorissen and Ringer, Ber., 39: 2095 (1906). 



■'■ S. C. Lind, The Chemical Effects of Alpha 

 Particles and Electrons, Chemical Catalog Co., 

 Xew York (1921). 



