LIME AND CEMEXT INDUSTRIES 6G5 



and the rest later, the lime becomes granular and lumpy. An 

 excess of water in slaking is also undesirable, as it tends to lower 

 the temperature of the mixture, and it is therefore well to use 

 hot water if this can be done conveniently. 



The hydration of lime powder or- slaking to a pasty mass must 

 be carried out very carefully, as otherwise, specially in the case 

 of overburned lime, some unslaked particles will remain, which 

 may slake later and make themselves unpleasantly prominent. 



As water is added to the lime, it gradually forms a stiff paste, 

 whose stiffness increases with the purity of the lime. 



With careful slaking, 1 cubic meter of fat lime gives 2.7 cubic 

 meters of paste and 1 cubic meter of lean lime gives 1.8 cubic 

 meters. 1 



The excess of water is gotten rid of in part by evaporation 

 and is also drawn off, while the slaked, pasty mass is allowed to 

 stand in the pit to insure thorough slaking of every particle 



In the pits lime will hold itself for a long time without change 

 provided it is properly protected from the air, but the damp lime 

 paste absorbs carbonic acid greedily with the formation of car- 

 bonate of lime, which solidifies. The crust of calcium carbonate 

 which forms is very thin, but it prevents the action from con- 

 tinuing farther in the mass. The solidifying action of the lime 

 alone is of little importance and becomes of value oniy when 

 sand is added. The use of the sand presents large masses or 

 lumps of the lime from collecting in any one spot and not be- 

 coming thoroughly converted into the carbonate. 



Quicklime is a strong base and absorbs water with the greatest 

 avidity, and in water it forms a milky liquid known as milk of 

 lime. 



On the other hand, quicklime can be made by adding the lumps 



of lime piece by piece to the water till a strong paste is formed 



by stirring the mass. The stirring is specially necessary in the 



case of lean limes. 



»Tn order to assist the slaking of such lean limes, it has been 



found advisable to use only one third the necessary amount of 



1 S jhoch, C. Die moderne auf bereitung und wertung der moitel-iiiaterialh'n, 

 p. 59. 



