182 Proceedings of Indiana Academy of Science 
amalgams of thallium, indium and tin. Meyer’ has used a hydrogen 
coulometer for similar work. 
The validity of the above assumption regarding lead has seemed 
questionable, and the purpose of the present work has been to ascer- 
tain, first, the relative amounts of the two deposits; and, second, the 
relation between each of these amounts and the amount of silver de- 
posited in a silver coulometer placed in the circuit in series with the 
cells containing the solution of lead nitrate. The latter quantities 
should enable one to answer the question as to whether there is de- 
posited in the mercury a weight of lead equivalent to the weight of 
silver deposited in the coulometer, and, therefore, whether one can cal- 
culate the per cent of lead in the amalgam from the amount of silver 
deposited. 
Previous Work. Although “Lead most readily of all the elements 
forms oxide on the anode during electrolysis,” there is a considerable 
tendency for this element to separate from an aqueous solution of the 
nitrate partly as metallic lead on the cathode and partly as lead per- 
oxide on the anode. Various individuals’ have noted this division of 
the lead between the two electrodes and have studied the factors in- 
fluencing the formation of the two deposits. Electrolysis from a neutral 
solution gives both the metal and the peroxide. An addition of nitric 
acid seems to improve the conditions for obtaining the peroxide; for 
with 15-20 per cent of the acid present, all the lead deposits in this 
form. Even with these higher concentrations of acid, however, a small 
amount of metallic lead may deposit, but it gradually dissolves as the 
decomposition proceeds. Easily oxidizable substances, such as lactose, 
glycerine, etc., hinder or prevent the formation of the peroxide. Oxalic 
acid, for example, is said to be very efficient for this purpose. 
In this earlier work there is included no mention of quantitative 
results on the relative amounts of the deposits of metallic lead on the 
cathode and lead peroxide on the anode, under the different conditions 
of electrolysis. Any of the quantitative determinations have been made 
with the aim of separating all the lead, either as peroxide or as the 
metal. 
Present Problem. The object of the present investigation has been 
the determination of the quantity of lead deposited at each electrode, 
under varying conditions of electrolysis, together with a determination 
of the quantity of silver deposited in a coulometer placed in the electrical 
circuit. This has involved, first, the arrangement of apparatus suitable 
for the electrolysis; and, second, the selection of satisfactory analytical 
1Z. Phys. Ch. 7, 481 (1891). 
2 Mathers—Trans. Am. Electrochem. Soc. 23, 178 (1913). 
3 Luckow—Z. anal. Ch. 19, 15 (1876); Ibid. 22, 485 (1883). 
Schucht—Ann. Chim. Phys. (5) 138, 508 (). 
Frechland—D. R. P. 140, 317; J. Ber. 9, 660 (1903). 
Thomidlsen—Chem. Ztg. 18, 1355 (1894). 
Vortmann—Ann. 351, 238 (1907). 
Gooch and Beyer—Am. Jr. Sci. (4) 25, 249 (1908); 27, 59 (1909), 
Fairchild—J. Ind. Eng. Chem. 3, 902 (1911). 
Smith—J. Am. Chem. Soc. 27, 1287 (1905). 
Tenney—Am. Jr. Sci. (4) 5, 413 (1883). 
