366 CEMENT MATERIALS AND INDUSTRY. [bull. l>43. 
Analysis of hydraulic lime, Konigshof, Germany. 
Lime (CaO) 81. 541 
Magnesia (MgO) 1 . 751 
Soda (Na 2 0) 211 
Silica (Si0 2 ) 12.421, 
Alumina ( A1 2 3 ) -• <>-0 
Iron oxide (Fe 2 3 ) 883 
Manganese oxide (Mn0 2 ) Trace. 
Carbon dioxide (C0 2 ) 194 ; 
Moisture ( H 2 ) 425 
DRYING AND SLAKING THE LIME. 
The granulated slag, as it comes to the mill from the tanks to which 
it is carried in granulating it, holds a very large percentage of water. 
The amount of water carried will vary in practice at different plants 
between 25 and 50 per cent as limits. Early in the history of slag- 
cement manufacture attempts were made to utilize this surplus water. 
To this end the wet slag was mixed with dry unslaked lime, the expec- 
tation being that the water in the slag would serve to slake the lime. 
In practice, however, it was soon found that this plan was not success-J 
ful. The lime was only partially and very irregularly slaked, and 
the mixture was not left in such a condition as to be economically J 
handled by the pulverizing machinery. In present-day practice, there- 
fore, the lime is slaked before it is mixed with the slag. 
The slaking is done with the minimum possible amount of water, so 
as to leave the slaked lime in the form of a fine, dry powder. 
SIEVING AND GRINDING THE LIME. 
If lime has been thoroughly burned and carefully slaked it will all 
be in the form of a very fine powder, much finer than can be obtained i] 
by any economically practicable grinding machinery. In practice, 
however, it will be found that the lime after slaking has not all fallen j 
to powder but still contains a certain proportion of hard lumps. 
The degree of carefulness with which the burning and slaking have 
been conducted may be roughly judged b}^ observing the relative 
proportions of lumps and powder. 
The material remaining as lumps is of three different kinds. First 
and in greatest proportion, are fragments of limestone which have 
not been thoroughly burned in the kiln. Such unburned pieces would 
be inert if used in the cement. Second, part of the lumps represent 
fragments of limestone which have been overburned in the kiln, 
and have therefore partly clinkered. This is particularly likely to 
happen if the limestone contained any large proportion of silica or 
alumina. These partly clinkered lumps, being really poor-grade 
natural cements, can, if pulverized, do no particular harm to the slag 
