ECKEL.] 
PUZZOLAN CEMENTS. 
3(>1 
Steel Company slags have been selected from a large series to show 
CaO 
the extreme ranges of the different elements. The ratios ov . and 
*I* 3 have been calculated for each slag- and are shown in this table. 
Si0 2 * 
From these data it can be seen that the ratio of alumina to silica is 
arried very high atChoindez; and is rather low at Chicago, relatively 
:o most of the European plants. It must be remembered, however, 
:hat one reason for carrying a high alumina-silica ratio does not apply 
it Chicago, as there rapidity of set is gained by the use of the Whiting 
process. Taking these two plants as representative of the best Euro- 
jean and American practice, the average of the analyses given shows 
CaO 
atios actually used to be: Choindez, Switzerland, q|?y= 1.71, 
lc r 
MX\ 
CaO 
ALA 
Si() -0.90; and Chicago, 111., g iQ - = 1.49, g{fcr = 0.44. 
These results may be compared with the theoretical ratios advised 
>y Tetmajer, Prost, and Mahon. 
Analyses of slags used in slag cements. 
Silica 
(SiOj). 
Alu- 
mina 
(AL0 3 ). 
Iron 
oxides 
(FeO, 
Fe 2 3 ). 
Lime 
(CaO). 
Mag- 
nesia 
(MgO). 
Lime 
sul- 
phide 
"(CaS). 
Lime 
sulphate 
(CaS0 4 ). 
Sul- 
phur 
(S). 
Sul- 
phur 
triox- 
ide 
(SO,). 
Ratio. 
Ca( > 
sin./ 
Ratio, 
AL0 8 
SiO-2 
1 . 
2 
3 
4 
5 
6 
7 
8 
9 

I 
30. 00 
31. 50 
32.90 
31.50 
26. 88 
27. 33 
26. 24 
32.20 
33. 10 
31.80 
31.30 
28. 00 
18. 56 
13. 25 
16. 62 
24. 12 
23. 81 
24.74 
15. 50 
12.60 
14.80 
14. 76 
0.75 
.46 
.62 
.44 
.63 
.49 
32. 75 
42.22 
47.30 
46. 10 
45.11 
45. 83 
46.83 
48.14 
49.98 
49.74 
48.11 
5. 25 
3.18 
1.37 
1.90 
3.42 
1.09 
1.31 
1.41 
1.16 
1.68 
1.67 
1.7s 
1 . 49 
1 . 51 
1.56 
1.10 
0. 93 
0. 45 
2. 21 
.59 
.41 
. 52 
1.09 
. 92 
.88 
2. 27 
2 45 
1.86 
1.34 
.59 
.S9 
0. 17 
.32 
.87 
.93 
.48 
38 
2. 29 
. 16 
2. 66 
. 13 
1, 2. Middlesborough, England. 
3. Bilbao, Spain. 
4. Saulnes, France. 
5. 6, 7. Choindez, Switzerland. 
8, 9, 10, 11. Chicago, 111. 
The erection of a slag-cement plant in connection with an} T given 
urnace is not justified unless a sufficient amount of the slags usually 
>roduced will fall within the slag-cement requirements, which have 
>een outlined above in the section on chemical composition of the 
lag (?). In a large plant it will usually be easy to secure a constant 
upply of slag of proper composition without interfering with the 
>roper running of the furnaces. In a small plant, however, or in one 
unning on a number of different ores, such a supply may be difficult 
