TECHNICAL CHEMISTRY. 



335 



In place of the old black-ash furnace or balling-furnace 

 in which the reaction is completed by hand-labour, a new 

 furnace, termed a revolving black- ash furnace, is being now 

 largely employed. A representation of such a revolving fur- 

 nace is seen in Fig. 14. In this the mixing of the materials 

 is effected mechanically. The charge, usually consisting of 

 30 cwt. of salt-cake, 32 of limestone, and 20 of slack, is 

 introduced by means of a hopper into the large cylinder, B, 

 placed horizontally. Through the axis of this cylinder, 

 B, names from a furnace, A, Fig. 14, are allowed to pass. 



Revolving Black, ^-AsJv Furnace 



A. Furnace. 

 JB .ReroU-er. 



C. Engine. 



D.B oiling -doH'Ti' 



fans. 

 E Drainers. 



i Side, Elevaliorv 



Section, t/trow/hs JL 



Fio. T4. 



This cylinder revolves first at a slow rate, and afterwards 

 with an increasing velocity, finally reaching a maximum 

 of five or six revolutions per minute. The cylinder is 

 10 to 12 feet in diameter and 15 to 18 feet long. Each 

 charge takes about two hours to work off, and when com- 

 pleted the door seen in the side of the cylinder is opened 

 and the fused mass allowed to flow into the iron trucks 

 placed beneath it. It yields 10 balls, each being a small 

 truckfull of black-ash, weighing 3 cwt. 



The advantages which the revolving black-ash furnace 

 has over the hand-worked ones chiefly consist in the saving 



