Lead and Lead Peroxide 187 
the errors resulting from drying the peroxide at a temperature too 
low to expel all the water, and from the oxidation of the amalgam 
during washing and drying. The former values are then too high and 
the latter too low, thus increasing the ratio of the former to the lat- 
ter. No nitric acid was used in these determinations. i 
Table I does not include the deposits of copper in the coulometer. 
It will be noted in these earlier results that the ratios of the deposit 
of lead at the anode to that at the cathode are distinctly higher and 
more variable than is the case with the new results for Series I shown 
in Table II. 
Discussion of Results. As shown in Table II, the results for solu- 
tions containing free nitric acid are so variable for the different ex- 
periments and so inconsistent for the two cells in each experiment, 
that one seems justified only to conclude the action of some variable 
and uncontrolled factor. However, even from these acid solutions, the 
deposits of lead at both the anode and cathode are approximately equiva- 
lent to the corresponding deposit of silver, and also, for a distinct 
change in concentration of nitric acid, there is not any marked change 
in the ratio of the amount of lead deposited at the anode to that de- 
posited at the cathode. 
For the experiments in which no nitric acid was added to the solu- 
tion of lead nitrate, the results are distinctly less variable, both for the 
separate experiments and for the two cells in each experiment. Using 
some variation in the amperage for the different experiments, and 
with a considerable difference in the time each ran, there is a fair 
constancy in the ratios for each of the two deposits of lead to the 
silver in the coulometer, and, consequently, for the one deposit to the 
other; and also there is a fairly satisfactory agreement in the amount 
of the deposits in the two cells. It will be noted that, with one excep- 
tion, the amount of lead found in the anodic deposit was always more 
than the lead equivalent of the silver, and that in the cathodic deposit 
was always less. 
Apparently, then, for the solutions made up by dissolving lead 
nitrate in water, one must conclude either that there is not deposited 
(under the conditions maintained in this work) at the cathode or at 
the anode an amount of lead equivalent to the amount of silver, the 
former being less and the latter greater; or that some error in the 
manipulation of the apparatus or in the methods of analysis has pre- 
vented the recognition of the deposit of an electrochemical equivalent 
of lead at either of the electrodes. 
The average of the ratios of the lead deposited at the anode to 
the lead equivalent of the silver is 1.0053 for the eight experiments; 
and for the cathodic ratio the average is 0.9864. These averages indi- 
cate the deposition at the anode of an amount of lead 0.5 per cent 
more, and at the cathode 1.4 per cent less, than the electrochemical 
equivalent of the silver. The variation of the individual ratios from 
these averages is approximately 0.5 per cent. 
In considering the explanation of the cause of these variable re- 
sults, one comes first to the question of the accuracy of the coulometer. 
Many careful researches have resulted in the adoption of the porous 
