180 BULLETIN 12, UNITED STATES NATIONAL MUSEUM. 



GLENDALE ZINC WORKS. 



These works are situated just south of St. Louis, Missouri, on the 

 bank of the Mississippi River. They treat a variety of ores both oxi- 

 dized and sulphide. The smithsonite ore comes from Jefferson Couutj^, 

 the calamine from Granby, Newton County, and the blende from the 

 Joplin district. The smithsonite is calcined, the calamine is hand- 

 dressed, and the blende crushed and jigged at the mine. The blende, 

 as received from the separating operation, is wet ; a portion of it is there- 

 fore dried and mixed hot with the remainder. It is crushed to pass an 

 8 mesh wire-cloth screen, and is then roasted to remove sulphur. 



The roasting furnaces are two storied — that is, contain one hearth 

 above another. As soon as the charge next to the fireplace has been 

 completely roasted it is withdrawn from the furnace, the other charges 

 are then moved up, and a fresh one introduced on the coldest hearth, 

 through an opening in the roof. Every 15 or 20 minutes the ore is 

 stirred. The six furnaces vary in size and contain charges of different 

 weights, four charges being in each furnace all the time, two on each 

 hearth. Roasting causes a loss of weight of about 15 per cent, of the 

 ore. The lump calamine ore as received is first calcined in a kiln sim- 

 ilar to a lime-kiln to remove water, four bushels of coal slack being 

 used per ton of calamine. It is then crushed to pass a 5 mesh wire- 

 cloth screen. The smithsonite is crushed to pass the same screen. 



To reduce the zinc in the retorts slack coal frooi the Big Muddy vein 

 is used on account of its low percentage of sulphur. 



There are eight Belgian furnaces, built in pairs ; four large ones, con- 

 taining one hundred retorts in nine rows, four small ones, containing 

 one hundred and four smaller retorts in nine rows. The closed ends of 

 the retorts rest on shelves projecting from the wall that divides the 

 two furnaces. The open front end is about 4 inches lower than the back 

 and rests on 2^ inch tile. These tiles rest on tile pillars which form the 

 front of the furnace. After the retorts have been introduced all the 

 openings in the front of the furnace are luted up with clay. Each fur- 

 nace has a fire-place at each end, and each pair of furnaces has a com- 

 mon draft stack. 



About 5 o'clock every morning preparations are commenced for 

 charging the retorts. Any cracked or damaged retorts are first re- 

 moved and new ones inserted, about three being replaced every 24 hours; 

 then, commencing at the top row of retorts, the condensers are removed 

 and cleaned. When they have been used so long that they can not be 

 cleaned any more they are broken up. The parts containing zinc are 

 broken off and added to the charge and the clean portions are ground 

 up and used in making retorts. Eight new condensers are required for 

 each furnace every 24 hours. 



After the condensers are removed the residues remaining in the re- 

 torts are raked out and the retorts cleaned, when they are ready for 

 charging. The charge has been made up on the day before. For the 



