126 



CEMENTS, LIMES, AND PLASTERS. 



to the water at once, or part may first be mixed with an excess of water 

 and then the remainder of the lime added. In the well-known Dodge 

 process the first plan is followed. In the Eldred process (U. S, Patent 

 721,871), in which the second plan is followed, the average amount of 

 lime handled at one slaking is half a ton (1000 Ibs.). Of this amount 

 about 400 Ibs. is first mixed and slaked with 450 to 500 Ibs. water, 

 and then the remaining 600 Ibs. of quicklime is added to the resulting 

 paste. A slaking-pan of the Walker & Elliott type is used. 



The Campbell hydrater, shown in Fig. 25, has been successfully used 

 at several lime-hydrating plants. The following data on its size, capacity, 

 power, etc., are taken from a recent catalogue of the Clyde Iron Works. 



TABLE 44. 

 CAPACITY, POWER, ETC., OF CAMPBELL LIME-HYDRATER. 



The amount of water used will vary with the character of the lime. 

 If it is a pure high-calcium lime, more water is added than if it contains 

 any considerable percentage of either magnesia or clayey matter. In 

 one process, for example, 55 Ibs. of water is added to each 100 Ibs. of 

 high-calcium lime, or 30 Ibs. water to 100 Ibs. magnesian lime. 



Sieving the product. After slaking the product is usually stored in 

 bins for forty-eight hours or so, after which it is ready for use. Before 

 packing, however, the coarser particles are removed either by screen- 

 ing or through use of an air separating device. When screens are used, 

 a 50-mesh is the common grade, the pitch of the screen surface being 

 changed to obtain whatever fineness is required. The Jeffrey Columbian 

 Separator, which has been used for this purpose, is described in the table 

 below. 



TABLE 45. 

 DETAILS OP JEFFREY SEPARATOR. 





