4 BULLETIN 283, U. S. DEPARTMENT OF AGRICULTURE. 
furnaces having grates compesed of single square bars which can be 
turned on their longitudinal axes to let the cinders down into the 
ash pits. Such furnaces hold from 3 to 5 tons each and are arranged 
in batteries of 20 to 25 for each set of lead chambers. The daily 
charge for each furnace when the system is in operation is from 
750 to 1,000 pounds of pyrites. The burners for the pyrites “fines” 
consist of cylindrical furnaces having a series cf shelves so arranged 
that the burning material can be mechanically raked from shelf to 
shelf until the fully burned cinder is discharged at the bottom of 
the furnace. The rakes are attached to a central air or water cooled 
shaft. In one type of furnace the shaft revolves; in another the 
shaft is rigid while the furnace itself revolves. 
The gases from the pyrites burners are forced into a dust chamber 
fitted with baffle plates where the oxides of iron, arsenic, lead, zinc, 
etc., are in a large measure removed. From the dust chamber the 
gases enter the Glover tower, which consists of a lead tower (usually 
from 20 to 30 feet high and 6 to 8 feet across) lined with acid-resisting 
brick and partly filled with quartz or other acid-proof material so 
arranged that the dilute nitrous vitriol which is distributed from an 
apparatus at the top of the tower will trickle down through the 
interstices. The heat of the burner gases which enter the Glover 
tower at a temperature of from 300° to 400° C. drives off water and 
the oxides of nitrogen from the nitrous vitriol, restoring them to the 
system. The uses of the Glover tower therefore are threefold: first, 
to cool the furnace gases before allowing them to enter the lead chamb- 
ers; second, to restore water and the oxides of nitrogen to the system; 
and third, to produce an acid more concentrated than that formed 
in the lead chambers. 
From the Glover tower the gases enter the first of the lead chambers 
where most of the sulphuric acid is made. The lead chambers usually 
consist of large square or oblong boxes made of sheet lead (weighing 
from 6 to 8 pounds per square foot) and having a capacity of from 
25,000 to 75,000 cubic feet. Water ii the form of fine spray or 
steam is introduced into the chambers at various pomts. This 
decomposes the nitrosulphuric acid formed into sulphuric acid and 
returns the oxides of nitrogen to the system to be agai acted upon 
by the furnace gases. The number and size of the chambers used 
vary from 2 to 10 or more, depending on the number and size of the 
pyrites burners. Where the quantity of sulphur burned daily is 
large the acid plant is often divided into separate units, each battery 
of burners furnishing gases to its own set of lead chambers. The 
gases pass from the first to the second chamber and so on through 
1In the Meyer Tangent system the lead chambers are cylindrical in form, while in the Falding system 
their height is several times their length and width. 
