688 CEMENTS, LIMES, AND PLASTERS. 



sticking to them. Around each of the molds thus formed is a space 

 0.20 m. wide, through which the slag flows. When all the partitions 

 are in place, the bottom of each mold is made flat by pressing down 

 into it a piece of sheet iron (of the same size as the compartment), 

 attached to a handle. 



When the molds are ready slag is brought from the furnace in slag 

 wagons, and allowed to flow through the interspaces and into the molds. 

 When the slag has about half filled a mold, a little sand is thrown on 

 it to prevent too rapid cooling. When the molds are entirely full, 

 they are covered with about a foot of sand and allowed to stand for 

 forty-eight hours. At the end of this time the slag is cool, the sand 

 is shoveled oft 7 , and the iron partitions removed. 



During rainy weather the molding ground is kept covered with 

 boards until the slag is ready for pouring, and as soon as this operation 

 is finished the molds are again covered with boards. 



The blocks are usually cubes, 0.15 m. on the edge, though larger 

 sizes and different shapes are occasionally cast. The material which 

 has solidified in the spaces between the molds is broken up for use as 

 road metal. 



At Koch Hutte similar processes are employed. Large blocks, 

 however, are cast in cast-iron molds, with a cover that is shut down 

 in order to compress the slag. Similar work is carried on at Kupfer- 

 kammer Hutte. 



Analyses of typical slags from the Mansfeldt district are given in 

 Table 251. 



A very interesting example of the manufacture of slag blocks or 

 tiles from a copper blast-furnace slag has been described * by Braden 

 as having been seen in operation at a furnace located near' Santiago 

 de Chile. His description is as follows: 



The slag and matte are tapped from the blast-furnace into a slag- 

 pot. After settling for a few moments the slag is poured from ladles 

 into molds which are 6 inches square and 1 inch deep. The molds 

 after being filled with slag are placed on a hearth which has a movable 

 cover, and covers are placed on the molds as well as on the hearth. 

 A very light heat is kept up, so that the slag cools very slowly. When 

 it appears black the molds are lifted from the hearth and the slag tiles 

 are dumped into cold water. The tiles thus made are very light and 

 portable. When laid they have proven to be tough and durable. 

 For this manufacture a slag carrying a considerable excess of iron 



* Trans. Am. Inst. Min. Engrs., vol. 26, pp. 52-53. 1896. 



