METHODS OF MANUFACTURE. 
Analyses of cerm nl mixtures. 
53 
fclica (Si0 2 ) : 12. 62 
Llumina I A1 2 3 ) ail(1 irun nxi,le (FeO) 6.00 
ame carbonate I ( ';i( !0 3 ) 75. 46 
lagnesia oxide I Mg< )) 2. 65 
13.46 
73.66 
(?) 
:{ 
13.85 
7.20 
73. 93 
(?) 
1-1.77 
4.35 
76.84 
1.74 
BURNING THE MIXTURE. 
After the cement mixture has been carefully prepared, as described 
preceding pages, it must be burned with equal care. Jn the 
fly (lav> of the Portland-cement industry a simple vertical kiln, 
Inch like that used for burning lime and natural cement, was used 
>r burning the Portland-cement mixture. These kilns, while fairly 
fficient so far as fuel consumption was concerned, were expensive in 
hor. and their daily output was small. In France and Germany 
lev were soon supplanted by improved types, hut still stationary and 
rtical, which gave very much lower find consumption. In America. 
jiwever, where labor is expensive, and find is comparatively cheap. 
n entirely different style of kiln has been evolved. This is the rotary 
iln. With the exception of a very few of the older plants, which 
ive retained vertical kilns, all American Portland-cement plants are 
>w equipped with rotary kilns. 
The history of the gradual evolution of the rotary kiln is of great 
iterest. and is discussed in the papers listed below: 
Duryee, E., The first manufacturer of Portland cement by the direct rotary-kiln 
bcess: Engineering News, July 26, 1900. 
Lesley, K. \V.. History of the Portland-cement industry in the United States. 
ti pp. Philadelphia, L900. 
Lewis, F. 1L, The American rotary-kiln process for Portland cement: Cement 
idustry, pp. 188-199, New York, 1900. 
Mattiiey, LL, The invention of the new cement-burning method: Eng. Min. Jour., 
»1. 6 . L899, pp. 555, 705. 
Bfanger, \Y. LL, and Blount, P>., The rotary process of cement manufacture: 
roc. Inst. Civil Eng., vol. 145. 1901, pp. 44-136. 
The influence of the rotary kiln on the development of Portland-cemenl manu- 
stnre in America: Engineering News, May 3, L900. 
Tlie design, construction, and operation of the vertical stationary 
Bus of various types are discussed in many reports on Portland 
nient. but as the subject is. in America at least, a matter of simply 
storical interest, no description of these kilns or their operation will 
given in the present bulletin." 
Perhaps the mosl satisfactory single paper <>n this subject is that by Stanger, W. EL, ami Blount, 
, Gilbert, W.. ami Candlot, E., ami others I Discussion of the value, design, ami results obtained from 
nous types of fixed kilns). Proc. lust, civil Eng., vol. 11".. 1901, pp. Mh18, 81-82, 95-100. 
