178 ANNUAL REPORT 
The expulsion of carbon dioxide from a kaolin-calcium carbonate 
mixture is pictured rather clearly by the accompanying curve* repre- 
senting the per cent. of the original weight of briquettes, made up from 
70 parts of kaolin and 30 parts of whiting (calcium carbonate) remain- 
ing after heating at different temperatures. The time occupied by the 
experiment was 28 hours. The temperature was increased steadily up 
to 725°, when this heat was maintained for a little over 12 hours to’ 
observe the effect of heat soaking on the briquettes. The temperature 
was then raised steadily to t0o00°. In this curve the interesting fact was 
brought out that while in pure kaolin the chemical water is expelled 
between 450° and 600°, the carbon dioxide from the briquettes contain- 
ing 30 per cent. of the carbonate will prolong the dehydration to goo’. 
Heat soaking for a comparatively long period is of no advantage, for, 
though it drives off some additional carbon dioxide, this amount is but 
small. This agrees with the laws of phase rule. 
Investigations Carried on by the Writer.—In order to study 
further the effect of composition and temperature of burning of the 
Roman cement type on the resultant hydraulicity the following series was 
projected and carried out by the writer. Two clay bases were prepared, 
one consisting of almost pure kaolin and one of a mixture of kaolin and 
very fine ground quartz, passing a-150 mesh sieve, made up from 56 parts 
of kaolin, and 44 of quartz. Accordingly, the composition of the two clay 
bases was: 
Kaolin 
quartz 
: Kaolin. mixture. 
STN Teas iat Li tele MRE ee ae a eT Me at aon EOSaE 70.0 
PN Nb aah oy: ene raM MMMM Int el Thar arc at Pee ti heal eo) 39.7 DADH Op 
CIE MWA TET eat Ee CRE 1B 3 God 
99.9 99.9, 
Starting with each clay base and using a pure grade of commercial 
calcium carbonate, four mixtures corresponding in composition to the 
following four formulce were prepared by grinding wet in a porcelain 
lined ball-mill: 
(2.5CaO)SiO ,(CaO) Al ,O, 
(2.0Ca0)S8i0 ,(CaO)A1,0 , 
(1.5CaO)SiO ,(CaO)AI,0, 
(1.0Ca0)Si0 ,(CaO)Al,0 , 
These eight cements formed one-half of the series, while the other half 
consisted of mixtures based on the same two clays, but built up with a. 
dolomitic materia! in place of the calcium carbonate. This dolomite was 
*W. M. Kennedy, Transactions Am. Cer. Society, Vol. IV. 
