UTAH ACADEMY OF SCIENCES 229 
tion caused to take place between the chloridizing re- 
agents and the metal bearing minerals. The metallic 
haloids thus formed are volatilized and carried away, by 
the furnace gases. 
DUST CHAMBERS. 
The gases from the furnace are passed through 
suitable dust chambers where the heavier dust particles 
that were mechanically carried from the charge are 
deposited; this dust being recovered and returned to 
the furnace. 
FUME PRECIPITATION. 
From the dust chambers the gases carrying the metal 
chlorides are passed through a Cottrell electrostatic pre- 
cipitator, where the metal chlorides together with all 
other solid constituents are deposited. 
There are several types of electrostatic precipitators, 
the most common of which is the tube treater. The so- 
called pipe or tube treater is quite simple in construction; 
the essential features being an iron pipe usually four 
or six inches in diameter with an insulated metal wire 
suspended through the center. The suspended wire is usu- 
ally charged with 25,000 to 50,000 volts of direct cur- 
rent electricity, while the pipe is simply connected to the 
ground. The electrostatic pressure on the insulated wire 
causes an electric corona brush discharge which sweeps 
the gases clear of all solid constituents. 
METAL CHLORIDE FUMES. 
The character of the product from the treaters 
depends on the metal values carried in the ore. In gen- 
eral, however, the metals thus recovered are present as 
chlorides, oxychlorides or in the elemental form. Gold is 
usually present in the latter state. Other constituents 
of the fume may be small quantities of iron, lime and 
insoluble, together with relatively large quantities of 
salt (sodium chloride). Considerable salt is dissipated 
during the roast, which is due to hydrolysis or direct 
evaporation. 
