28 
CHEMISTRY: BAXTER AND HARTMANN 
tended over about eight hours. At the end chlorine had nearly ceased to 
be evolved at the anode, although some residual conductivity remained, 
owing to the formation of a small amount of perchloric acid. Toward 
the end of the electrolysis the column of bulbs and the walls of the cell 
were several times rinsed into the cell. At the completion of the electrol- 
ysis the electrolyte was displaced with water which had been freshly 
saturated with hydrogen; and the water in turn was displaced with pure 
alcohol, the maximum voltage being maintained between the electrodes 
during the operations, and care being taken not to break the electrolytic 
circuit. The cell was then placed in a desiccator containing fused potas- 
sium hydroxide, the pressure in the desiccator was reduced to a few milli- 
meters of mercury with a mechanical pump, and the cell was allowed 
to stand until the alcohol had evaporated. The cell was next trans- 
ferred to a second desiccator which contained the counterpoise of the 
cell, and the two were allowed to stand in a low vacuum for some hours 
before being weighed. Further standing in an exhausted desiccator 
produced no change in weight, showing both that the cell and amalgam 
were dry and that the amalgam had httle tendency to oxidize. The 
rinsings, both aqueous and alcoholic, were evaporated in a quartz dish 
with a very small amount of redistilled sulphuric acid; and, after trans- 
ference to a weighed platinum crucible, the residue was ignited at dull 
redness. In this way a residue, in most cases weighing less than one 
milligram, was obtained which was shown to be cadmium sulphate. 
A correction to the weight of cadmium was applied upon this basis. 
Complete precipitation of the cadmium was never secured, although, 
according to the experience of Quinn and Hulett, no cadmium is left 
undeposited, even when a relatively large amount of sulphuric acid is 
present. The small amount of free chlorine contained in the residual 
electrolyte in our experiments may have been the cause of the incomplete 
deposition of the metal. 
The weighing-bottle containing the boat and the electrolytic cell were 
both weighed by substitution for a counterpoise very similar in con- 
struction and of the same total volume. 
The experimental data and the results calculated from them (assum- 
ing the atomic weight of chlorine to be 35.457) are shown in the accom- 
panying table. The weights here given have been reduced to the vacuum 
standard by applying the following corrections for each gram of sub- 
stance: cadmium chloride, -f- 0.000152 g, cadmium dissolved in mer- 
cury, - 0.000016 g. 
It will be seen that this research has yielded a value (112.417) for the 
atomic weight of cadmium in very close agreement with the earlier one 
