108 CEMENTS, LIMES, AND PLASTERS. 



He further estimated that at the current prices (1871) of labor 

 and fuel in the United States, lime could be manufactured in a Hoff- 

 man kiln at about $2 per ton, the following details of cost being 

 given : 



Cost of quarry and plant $20,000 



Annual yield of kiln, tons 20,000 



Per Ton Lime. 



Interest on investment $0.07 



Quarrying stone . 65 



Charging kiln . 20 



Drawing kiln 0.15 



Wages of burners 0.15 



Fuel . 43 



Contingent expenses, 20 per cent . 33 



$1.98 



Utilization of carbonic-acid gas from lime-kilns. During the burn- 

 ing of limestone to lime an enormous amount of carbonic-acid gas 

 (carbon dioxide, C0 2 ) is driven off and usually wasted. The extent of 

 this waste may be appreciated when it is recalled that 100 Ibs. of pure 

 limestone would give on calcination 56 Ibs. of quicklime and 44 Ibs. 

 of carbon dioxide. To put the matter in another way, for every ton 

 (2000 Ibs.) of lime made 1571 Ibs. of carbon dioxide are thrown into 

 the atmosphere. During the year 1903, therefore, over one and a 

 half million tons of carbon dioxide were produced and wasted from 

 the lime-works of the United States. Few attempts have been made 

 by lime-manufacturers to utilize this valuable by-product, though the 

 manufacture of carbonic acid, as an independent industry, has become 

 of great importance. 



Mr. Henry A. Mather states * that carbon dioxide from lime-kilns 

 "helps make profitable a well-rounded operation in Oldbury, England, 

 the only surviving chemical works using the Leblanc soda process. 

 The salt cake is burned in furnaces, the soda bleached out, the chlorine 

 recovered, and the sludge of partially decomposed carbonaceous matter 

 containing a large percentage of sulphite of lime is treated in closed 

 agitators with carbonic-acid gas obtained from burning lime rock in 

 a closed kiln. The hydrogen disulphide driven off in this operation 

 of precipitating the carbonate of lime is burned in a Klaus kiln, air in 

 proper proportions enters with the gas, and flowers of sulphur is the 

 final product of this part of the operation ". A further utilization of 

 by-products at this plant occurs when the carbonate of lime so pre- 



* Engineering and Mining Journal, March 29, 1902. 



