vi] PROPERTIES OF THE RADIATIONS 175 
Although the coloration due to radium rays extends deeper 
than that due to the cathode rays, when exposed to light the 
colour fades away at about the same rate in the two cases. 
Becquerel! found that white phosphorus is changed into the 
red variety by the action of radium rays. This action was shown 
to be due mainly to the B rays. The secondary radiation set up 
by the primary rays also produced a marked effect. Radium rays, 
like ordinary light rays, also caused a precipitate of calomel in the 
presence of oxalic acid. 
Hardy and Miss Willcock? found that a solution of iodoform in 
chloroform turned purple after exposure for 5 minutes to the rays 
from 5 milligrams of radium bromide. This action is due to the 
liberation of iodine. By testing the effect of screens of different 
thicknesses, over the radium, this action was found to be mainly 
due to the 8 rays from the radium. Réntgen rays produce a 
similar coloration. 
Hardy* also observed an action of the radium rays on the 
coagulation of globulin. Two solutions of globulin from ox serum 
were used, one made electro-positive by adding acetic acid, and the 
other electro-negative by adding ammonia. When the globulin 
was exposed close to the radium in naked drops, the opalescence of 
the electro-positive solution rapidly diminished, showing that the 
solution became more complete. The electro-negative solution was 
rapidly turned to a jelly and became opaque. These actions were 
found to be due to the @ rays of radium alone. 
This is further evidence in favour of the view that the a rays 
consist of projected positively charged bodies of atomic dimensions, 
for a similar coagulation effect is produced by the metallic ions of 
liquid electrolytes, and has been shown by W. C. D. Whetham* to 
be due to the electric charges carried by the ions. 
116. Gases evolved from radium. Curie and Debierne® 
observed that radium preparations placed in a vacuum tube con- 
tinually lowered the vacuum. The gas evolved was always accom- 
1 ¢. R. 133, p. 709, 1901. 
2 Proc. Roy. Soc. 72, p. 200, 1903. 
3 Proc. Physiolog. Soc. May 16, 1903. 
+ Phil. Mag. Nov. 1899; Theory of Solution, Camb, 1902, p. 396. 
5 ¢. BR. 132; p. 768; 1901. 
