192 Proceedings of Indiana Academy of Science 
PRESENT WORK. 
Oxidation of Lead Amalgams. As already stated, in the course of 
some work in this laboratory with lead amalgams, it was not found 
possible to handle them according to the method of Stahler and Alders 
without having marked evidence of oxidation, even with only a few 
hundredths of a gram of lead present. Amalgams prepared electrolyti- 
cally were always bright, and remained so during washing with water 
and alcohol. When washed with ether, however, there often formed 
on the surface of the amalgam a dark film which was easily lost on 
further washing. If washed immediately and quickly with the ether, 
not much of the film formed; but the longer the time of washing, the 
more film there was present. It was difficult to avoid losing it when 
washing by decantation; and if much was present, some was always 
lost. On standing any length of time following the washings with 
just water and alcohol, there was always considerable oxidation. 
To show this oxidation of the amalgam on standing, and the re- 
sulting loss in weight with washing, the following determinations are 
typical, except that the errors are considerably exaggerated due to the 
length of time the amalgams stood before washing. These amalgams 
were made up by dissolving a known weight of lead in a known weight 
of mercury and allowed to stand in a beaker 48 hours. After wash- 
ing with the liquids mentioned, the amalgams were dried in a desic- 
eator and reweighed, with the results shown in Table I. Numbers 1 
and 2 were washed once with 10 cc. of water and twice with 10 cc. 
portions of alcohol, while numbers 3 and 4 had, in addition to this, two 
washings with ether. 
TaBxe I. 
Loss in Weight of Amalgams During Washing. 
| 7 | 
No. Weight of Mercury Weight of Lead | Loss 
1 43.0182 0.8496 0.0138 
2 40.8870 1.0832 0.0076 
3 57.2745 1.0357 0.0162 
4 0.0227 
39.2819 0.8600 
Development of Method of Analysis. On account of the defects 
inherent in the methods already outlined for the analysis of lead amal- 
gams, it seemed desirable to have available a method for determining 
the concentration of the lead involving some procedure by which the 
element could be brought easily from the amalgam into aqueous solu- 
tion, and then determined gravimetrically in this solution. A solution 
of copper nitrate was selected as a promising possibility for obtaining 
the replacement of the lead in the amalgam by another element, thus 
bringing it into aqueous solution from which it could be precipitated. 
Copper sulfate was rejected because it brought about the formation of 
lead sulfate very shortly, which seemed to retard the replacement 
process. The procedure adopted consisted in covering the amalgam 
in a beaker with 25 cc. of a 10 per cent solution of copper nitrate for 
a period of 15 to 24 hours, decanting the solution, and washing the 
remaining amalgam. Copper is less soluble in mercury than lead, and 
