REVERSIBLE AND IRREVERSIBLE SYSTEMS UNDER INFLUENCE OF LIGHT. 363 
Thus we find that the. total E.M.F. ( i.e., the E.M.F. under the action of light at a 
constant temperature + the E.M.F. due to the heating of the exposed plate and 
liquid in front of it) of constant cells reversible in respect o f the cation is independent 
of the concentration of the AgN0 3 solution. 
A correction of 9 per cent, for the heating effect gives for the law of intensity and 
the volts obtained at a constant temperature the following data in («), ( b), (c). For 
the law of intensity we get:— 
In (a) 37 2 x 9'55 = 131 x 10 3 and 27 s x 16'83 = 12‘3 x 10 3 . 
In (b) 37 2 x 20'5 = 28*1 x 10 3 and 27 2 x 33’9 = 247xl0 3 . 
In (c) 37 2 x 2D4 = 29-3x10 3 and 27 2 x 36'4 =26-5xl0 3 . 
For the volts obtained we get : at 27 centirns. distance in (a) 33’OxlCT 6 volt, 
in (b) 34 - 9xl0 -6 volt, in (c) 36\3xl0 -6 volt. At 37 centirns. distance in 
(a) 18‘7 x 10" 6 volt, in (6) 21T x 10~ 6 volt, in (c) 2D3x 10~ 6 volt. 
§ 7. Experimental Residts obtained with Constant Cells Reversible in 
Respect of the Anion. 
I. The System (Ag-AgCl in Light, Decinormal NaCl Solution in Light, Decinormal 
NaCl Solution in the Dark, Ag-AgCl in the Dark). Plate NlO of June 30 
(10 Curves were taken), Table II. 
The Ag plates of the previous investigation (Ag plates in AgN0 3 solution) were 
covered on one side with shellac and paraffin, and coated on the other with an 
extraordinarily thin layer of AgCl by immersing them in water containing a merest 
trace of HC1 acid. A decinormal NaCl solution was brought into the quartz vessel, 
some AgCl was put on the bottom, then the Ag plates were fixed in the quartz 
vessel. Experimental data see Table II., pp. 392-393. 
The curves give a deflection to the left; the course of the induction ( b-c) and 
deduction periods ( d-e-f) show that the system is constant, gives no polarisation. 
After the induction period has passed, a constant E.M.F. (c—d) is obtained (whether 
the whole light or coloured screens are used). On removing the light from the 
system it returns, passing the deduction period, to its former state in the dark, as is 
to be seen from the straight line f'-f" reached by the system, which is a continuation 
of the straight line ci—b before the induction period. The current is flowing in the 
solution from the plate in the dark to the plate in light. The deflections obtained at 
a distance of the arc = 37 centirns. were : in Nl, 56 millims. (did not return 2 millims.); 
in N2, 53 millims. (corr. 55 millims.), average = 55'5 millims. = 59 x 10 -9 ampere 
= 51*8 x 10“" volt; at a distance of 50 centirns. : in N3, 31 millims. ; in N4, 34 millims.? 
average = 32 - 5 millims. = 34 - 6 x 10 -9 ampere = 30'4 x 10~ 6 volt. 
3 a 2 
