30 Gooch and Fairbanks—Halogens in Mixed Silver Salts. 
mass from above. The anvil keeps the crucible cool and tends 
to prevent the soaking of the asbestos with the fused silver 
salts, which would be disadvantageous in the washing process 
which follows the reduction. A rubber band cut from rubber 
tubing of suitable diameter is adjusted so as to cover the 
junction between the cap and crucible and make a water-tight 
electrolytic cell. When the electrolytic reduction is finished 
the band and cap are removed, the crucible is put upon the 
pump, the liquid is drawn through and the precipitate washed 
in the usual manner. 
It is obvious that the difficulty of washing out the sulphuric 
acid from the reduced silver may be avoided if it is possible to 
substitute for the sulphuric acid an electrolyte which, even if 
it were not easily removed by washing should be volatile at 
gentle heat without affecting the silver; and the danger arising 
from free chlorine may be obviated by taking care to have the 
chlorine absorbed by the electrolyte as soon as it is liberated. 
We find that twenty-five per cent alcohol containing a tenth 
of its weight of oxalic acid meets all the conditions for the 
electrolytic reductions of the mixed chloride and bromide of 
silver. Such a solution while possessing sufficient conductivity 
absorbs the free chlorine to such an extent that, as we have 
found experimentally no perceptible solvent action takes place 
upon the platinum and nothing remains in the silver reduced 
under such a solution which is not volatile at gentle heat with- 
out affecting the weight of the silver. 
In the test-experiments recorded in the accompanying table 
known amounts of silver chloride and bromide were precipitated, 
collected, washed, dried at 150°C., and weighed in the filtering 
crucible provided as usual with a layer of asbestos which was 
in this case covered with the perforated platinum dise. The 
_ cap was put in place, the crucible set upon an anvil, and the 
salts fused with a blowpipe flame in the manner described. 
The rubber band was adjusted, the crucible nearly filled with 
the ten per cent solution of oxalic acid in twenty-five per cent 
aleohol, and the current passed in the usual manner, the crucible 
serving as the negative electrode. When the reduction was 
judged to be complete the band and cap were removed, the 
crucible set upon the pump, and filtration of the liquid and 
washing of the residue carried out as usual. Finally the 
crucible, cap, and residue were ignited at a very low red heat 
and weighed. The entire treatment was repeated until the 
constant weight of the residue showed that the reduction was 
complete. 
