Gooch and Fairbanks—Halogens in Mixed Silver Saits. 29 
Electrolyte, Change in Change in 
15 em? of H.SO,, Strength of Time weightof weightof Connection 
(15 per cent) with current in in thecontain-_ wire elec- of 
the substance amperes. hours. ing crucible trode crucible. 
named. erm. erm. 
er orm. KI 0°46—0°25 24 0°0000 0°0000 Cathode 
j ‘79 
1 KBr —_0°50-—0°18 oD 0°0000 0:0000 Cathode 
4. « KCl  0-48—-0°18 26 0:0008— 0:0001— Cathode 
fae HCl bare i 0:0009*— 0:0000 Cathode 
on HCl 0°3 48 0:0004— 0°0004+ Anode 
So it appears that, while neither bromine nor iodine attacked 
the platinum perceptibly under the conditions of the experi- 
ments, though set free in abundance, an appreciable amount 
of the metal did dissolve under the action of chlorine. More- 
over the solubility seems to depend chiefly upon the area of 
surface exposed and not upon the electric polarity. The metal 
dissolved was reprecipitated by the action of the current only 
in the experiment in which, by reversing the direction of the 
eurrent and thus making the area of the anode large while that 
of the cathode was diminished, a corresponding increase of 
eurrent density upon the cathode was brought about. It is 
obvious that under ordinary conditions of electrolytic reduction 
the solvent effect of the chlorine upon the platinum will 
naturally produce an apparent deficiency in the weight of silver 
reduced. 
These sources of error in the electrolytic reduction of the 
fused silver salts we have endeavored to overcome. The 
danger of change in the constitution of the salts during prepa- 
ration for weighing we avoid by collecting them upon asbestos 
in a perforated crucible instead of upon paper ; but in order to 
secure perfect electrical conductivity throughout the mass of 
silver salts subsequently collected, dried, and weighed, we 
place a dise of perforated platinum foil upon the prepared felt 
of asbestos. In this way perfect electrical contact is obtained, 
though the rapidity of filtration is somewhat impaired. The 
disc also serves the useful purpose of preventing the disturb- 
ance of the felt by the gas evolved from the walls of the 
crucible in the electrolytic process.| When the silver salts 
have been collected, washed, dried and weighed, their fusion is 
effected by placing the capped crucible upon an anvil and 
directing the flame of a small blowpipe with care upon the 
* Platinum tested for and found in solution. 
+ This device has been suggested by Puckner (Jour. Am. Chem. Soc. 1893, 710) 
for holding down the asbestos in an ordinary jltration, and is no doubt of value 
when suitable asbestos is not at hand. A fairly good asbestos properly prepared, 
and deposited upon a perforated surface in which the holes are sufficiently 
numerous—best, as numerous as can be—does not, however, tend to rise during 
a filtration so long as the suction pump is in action.—F. A. G. 
