ECKEI,.] 
UTILIZATION OF IRON AND STEEL SLAGS. 
229 
fertilizers, alum, etc. Analyses of samples of these materials showed 
the following 1 compositions: 
Analyses of puddle slag and reheating cinder. 
Constituent. 
Puddle 
slag. 
Reheating 
cinder. 
FeO 
52.43 
19. 62 
6.41 
.81 
. 38 
16.39 
3.S4 
71.29 
Fe 2 O s .. 
MnO 
.21 
CaO___. 
ALA 
7.78 
Si0 2 _._ 
20. 06 
P,Or 
27 
S 
Trace. 
The slag was crushed in a Blake crusher to pass a three-fourths inch 
screen, and finally reduced in a Cyclone pulverizer to pass 225 mesh. 
The finest dust was used directly as paint stock. The coarser mate- 
rial, after treatment with sulphuric acid, was calcined and reground. 
This industry has been discontinued at Boonton, and it is believed 
that no slag is at present used for that purpose in the United States. 
ALUM. 
The preparation of alum from highly aluminous slags is accom- 
plished by means of the Lurmann process. So far the manufacture 
of alum by this process has not been attempted in the United States, 
though it has been carried out on a commercial scale in Europe. At 
Donjeux, France, the process has been employed in connection with 
the manufacture of slag cement, the gelatinous silica resulting from 
the alum-extraction process being used to accelerate the set of the 
cement. 
The Lurmann process, in brief, is as follows: Slags, as high in 
alumina as possible, are decomposed by means of hydrochloric acid. 
The resulting solution of aluminum chloride is treated with lime car- 
bonate, which serves to precipitate the alumina and any dissolved 
silica that may be present. In treatment with sulphuric acid the 
alumina is dissolved, leaving the silica. It is stated a that 100 kilo- 
grams of slag, containing 25 per cent of alumina, will yield 180 kilo- 
grams of alum and 31 kilograms of gelatinous silica. The silica is 
used in the manufacture of soluble glass and, as above noted, in the 
manufacture of slag cement. The process may even be profitably 
arrested after the first stage, as the aluminum chloride then obtained 
is marketable for use in certain sewage purification processes. 
« Wagner, Chemical Technology, p. 439. 
