46 Messrs. Wright and Thompson on the Determination of 
Here again, even in the most favourable instance, with the 
smallest current-density and platinum as — electrode, a con- 
derable amount of nonadjuvancy subsisted; for the value of 
CB, in this case was not greater than '001; so that the mini- 
mum counter E.M.F. set up was at least *448 volt, whilst the 
E.M.F. corresponding to the net chemical action is only "270 
volt, the heat-development being per gramme equivalent 
^(Ho, 0) . . = 34100 gramme-degrees. 
i(Cu,0,S0 3 aq) = 27980 „ „ 
6120 „ „ =-270 volt. 
It is hence evident, a fortiori, that when acidulated water is 
decomposed with two gold electrodes, the counter E.M.F. set 
up must be much greater for a given current-density than 
when two platinum electrodes are used, the deficiency in 
condensing-power being then manifest at both electrodes simul- 
taneously. The experiments described in Part IV. § 90 have 
shown that this is the case. 
146. In addition to the experiments above described as 
examples, a large number of analogous observations have been 
made with varying kinds of electrolytic solutions and elec- 
trodes, and with varying strengths of solutions. The general 
results of these experiments, so far as at present completed, 
may be thus summarized. 
(1) When an electrolytic cell is of such a nature that the 
counter E.M.F. set up is negative (i. e. when the cell is an 
electromotor), it is always found that the E.M.F developed is 
less the greater the density of the current generated. With very 
small current-densities the E.M.F. has a maximum value 
which in certain cases (e. g. Daniell's cell and the analogous 
zinc-cadmium and cadmium-copper cells described in Part VI.) 
is substantially identical with the E.M.F. corresponding with 
the heat-development due to the net chemical action taking 
place in the cell, i. e. with the E.M.F. representing the alge- 
braic sum of the chemical affinities involved. h\ certain 
other cases (e. g. the zinc- silver, cadmium-silver, and copper- 
silver cells described in Part VI.) the maximum E.M.F. de- 
veloped is sensibly below that due to the net chemical action. 
(2) Some kinds of combinations have been found to be 
capable of existing which can develop a greater E.M.F. than 
that due to the net chemical action (although the particular 
cells described by Favre as possessing this property are not 
really cases in point, Favre's results being due to experi- 
mental errors); amongst such combinations may be mentioned 
several where lead is the metal dissolved, i. e. lead-copper cells 
