230 TRANSACTIONS OF THE 
TREATMENT OF CHLORIDE FUMES. 
Three principal methods may be used for recovering 
the metals from fumes: 
(a) Reduction by fusion. 
(b) Leaching with subseqeunt precipitation. 
(c) Combination of leaching and fusing. 
The method employed will usually depend on the 
metal content of the fume; however, as each individual 
ore will constitute a problem, it is not feasible to discuss 
details of these methods in this paper. 
ORES IN GENERAL. 
TECHNICAL CONSIDERATION. 
The process may be applied to the treatment of 
both oxidized and sulphide ore. The latter, however, 
usually requires a preliminary desulphatizing roast, 
in case it should contain a high percent of sulphur. 
ARSENICAL ORES. 
Ores of any kind carrying appreciable quantities of 
arsenic, antimony, or bismuth, are readily treated by 
volatilization. The procedure is to give the ore a pre- 
liminary roast at about 850° C for the purpose of expel- 
ling the arsenic, antimony, bismuth, etc. This can usually 
be accomplished in about thirty minutes of heating, the 
fumes from the roast being recovered either in an elec- 
trostatic precipitator or by filtration of the gases through 
woolen bags. 
Basic fumes are best separated from basic gases by 
filtration through bags. In case the electrostatic precip- 
itator is used, there is a non-conducting film of the basic 
fume that covers the electrodes and prevents the essen- 
tial functioning of the corona discharge. What really 
happens is a condenser effect in which there is an inter- 
mittent building up of potential and electrical discharge 
which is not effective in precipitating fumes from gases. 
In the presence of an acid gas, basic fumes are readily 
precipitated electrostatically. 
