436 
on removing the salt from sunlight. This result is not surprising in 
view of the work of Seekamp * and others in which they demonstrated the 
powerful catalytic action which uranium salts displayed only while in 
the sunlight. 
The general action of sunlight is often such as to make chemical sub- 
stances better conductors of electricity.” Thus, in the sun’s rays, sulphur, 
phosphorus, selenium,® and mercuric sulphide’ are changed into modifi- 
cations which more easily conduct the electric current. Silver *® and 
gold ® oxides lose and lead oxide '® and manganous oxide" gain oxygen, 
each to give a substance which offers less resistance to the passage of the 
current. In aqueous solution the same facts are noted. Chlorine and 
bromine water give the respective halhydric acids; an aqueous solution 
of sulphur dioxide,’? even in the absence of free oxygen, is changed in 
the sunlight into sulphuric acid and sulphur; a solution of potassium 
iodide gives the better conducting potassium hydroxide ;™ ferric chloride 
with oxalic acid and with alcohol gives a mixture with increased 
conductivity, and the same is true of mercuric chloride in conjunction 
with ammonium oxalate.’ 
Hertz ** showed that a spark is formed much more easily in air when 
the spark gap is in the light than when it is in the dark, and Arrhenius * 
from his own work and that of Hertz on the conductivity of gases at 
low pressure under the influence of light makes the deduction that light 
has a tendency to ionize the air and thus to make it a better conductor. 
Mrs. Ayrton '* among many curious experiments demonstrated that a 
candle flame could discharge an electroscope very rapidly at a distance of 
40 centimeters. Many more instances can easily be added to this list. 
We believe there is here a more general relation which has not as yet 
been explained and therefore we expect to study these interesting 
phenomena in a much more exhaustive manner. For this purpose we 
have ordered apparatus of sufficient delicacy, but at the time of writing 
the proper instruments are not available in the Philippines, and for this 
‘Ann. d. Chemie (Liebig) (1862), 122, 113; (1865), 133, 253. 
'See J. Gibson, Ztsch. Phys. Chem, (1897) 23, 349. Arrhenius, Wien Akad. 
(1887) 96, 831. 
° Proc. Roy. Soe. (1889) 46, 136. 
7Heumann, Ber. d. chem. Gesell. (1874) 7, 750. Béttger, Chem. Centralbl. 
(1875) 291. 
8 Arrhenius, Wien. Akad. (1887) 96, 831. 
® Chevreul, C. R. (1858) 47, 1007. 
 Sechonbein, Edmann’s Journal (1850) 51, 273. 
1 Chastaing, Ann. Chim. Phys. (1876) (5) 11, 145. 
1 Tdem, JU. .c. 
"% Poge. Ann. (1863) 119, 497. 
™ Chastaing, /. ¢. 
1 Wien Akad. (1880) 80 (2) 636. 
” Hertz, Wied. Any. (1887) 31, 983. 
7 Arrhenius, Wied. Ann. (1888) 33, 643. 
8 Nature (1902) 65, 390. 
