4 BULLETIN 283, U. S. DEPARTMENT OF AGRICULTURE. 



furnaces having grates composed 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 of 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 1 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 in the form of fine spray or 

 steam is introduced into the chambers at various points. This 

 decomposes the nitrosulphuric acid formed into sulphuric acid and 

 returns the oxides of nitrogen to the system to be again 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 batten 

 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 



1 In the Meyer Tangent system the lead chambers are cylindrical in form, while in the Falding system 

 their height is several times their lenglh an<l width. 



