REVERSIBLE AND IRREVERSIBLE SYSTEMS UNDER INFLUENCE OF LIGHT. 375 
(b) A decinormal KBr solution was now used ; intensity of acetylene, calibration of 
Nalder N2 and Nl the same as in (a). The E.M.F. in the dark = 1’5 centims. to the 
left (1000 ohms shunt). The deflections obtained (with 1000 ohms shunt of gal¬ 
vanometer) were : in N3 = 120 millims., in N4 = 117, average = 118 ’5 millims. (at 
13°-5 C. and at 3.0 p.m.). 
(c) A decinormal NaBr solution was now used : intensity of acetylene = 47 millims., 
calibration of Nalder N2 and Nl the same as before ; the E.M.F. in the dark = 47 
centims. to the left (1000 ohms shunt of galvanometer). The deflections obtained 
(1000 ohms shunt of galvanometer) were : in N5 = 136 millims., in N6 = 112 millims., 
in N7 = 114 millims., in N8 = 114 millims. = average 119 millims (at 13°‘5). 
It follows from the above (1) that the E.M.F. of a combination reversible in respect 
of the anion is independent of the cation of the salt in solution ; (2) comparing the 
results obtained with the decinormal LiBr solution on July 25 and 20, we find that 
the Ag-AgBr plate kept the whole time in the dark is less sensitive to light than 
the plate which had been previously exposed several times to light ; (3) we find that 
the deflections of July 19 and 20 are essentially smaller than those of July 13 instead 
of being of the tame values or even of greater. The reason of this is probably that 
the Ag-BrAg plates were previously acted upon from the 15th till the 19th of July 
by BrH which gradually transformed the Ag (or Ag 2 Br) on the surface previously 
formed back into AgBr. 
(/3) The influence of the cation upon the E.M.F. obtained was again investigated 
between the 1st and 7th of February, 1905. Each of the plates was on one side 
covered again with shellac and paraffin. The plates had a thick coating of BrAg. 
On February 3 the sensitiveness of the plates reached already such a value that 
the E.M.F. seemed to change no more on further remaining in the dark, after previous 
illumination. 
February 3, 1905, Plate 16 
07 norm. KBr sol. gave : in Nl, 96‘5 millims. ; in N2, 96'5 millims. deflection ; 
07 norm. NaBr sol. gave: in N3, 85 millims. ; in N4, 86 millims. deflection. 
Intensity of acetylene = 20’05 right and left, Nalder N2 = 1575 centims., Nalder 
Nl = 1 9*2 centims. 
February 6, 1905, Plate 17 :— 
07 norm. NaBr sol. gave: in Nl, 84 millims.; in N2, 77 millims.; in N3, 
7 8 millims. deflection ; 
07 norm. LiBr sol. gave : in N4, 91 millims. ; in N5, 95 millims. ; in N6, 
91 millims. deflection. 
Intensity of acetylene = 21 '5, Nalder N2 = 16’05 centims., Nalder Nl = 19 - 2 centims. 
