28 Gooch and Fairbanks—Halogens in Mixed Silver Salts. 
easily, the bromide with less ease, and the iodide most difficultly 
—as might be predicted from a knowledge of the thermal 
values involved in the reactions. A current of hydrogen sul- 
phide charged with ammonium sulphide effects the complete 
conversion of silver chloride to silver sulphide at a temperature 
below 200°C ; but we have never succeeded in securing abso- 
lutely complete conversion of the bromide to the sulphide by 
similar treatment even at much higher temperatures, and the 
iodide resists conversion more obstinately than the bromide. 
Nor have we been able to find conditions under which the 
chloride may be converted while the bromide and iodide 
remain unattacked. In a study of the conditions best adapted 
to the reduction of silver salts electrolytically we have obtained 
results which point to advantageous modifications of the 
methods heretofore known. We find that the treatment of 
the fused salts may be simplified, made more accurate, and 
extended to mixtures containing silver iodide. 
In Kinnicutt’s process the difficulties lie, first, in the impossi- 
bility of destroying the paper, upon which the silver salts have 
been collected and washed, without affecting the conduction 
of the salts; secondly, in the obstinacy with which the spongy 
silver holds the sulphuric acid during washing; and thirdly, 
in the tendency of the chlorine liberated when a chloride is 
present to attack the electrodes. 
Upon the first point nothing need be said; the difficulty is 
obvious and well known. As to the second source of error, 
our experience shows that rapid washing is not sufficient to 
remove the sulphuric acid included in the reduced silver, even 
when excessive amounts of wash-water are used; but that a 
considerable time is indispensable for the escape of the acid 
‘from the silver to the wash-water by diffusion. In several 
cases we have found errors, ranging from a single milligram to 
six or seven, due to inclusion of the acid in residues which had 
been washed freely but rapidly, and which, even after ignition, 
yielded slowly hot water extracts which gave the test for a 
sulphate by barium chloride. 
The results of some experiments made to test the effect of the 
naeeree set free in electrolysis are shown in the accompanying 
table : | 
On Me ae oe ee Te 
