114 



PURIFIERS. 

 Fig. '25 (2). 



F and G being in the same partition communicate with each other, as do 

 H and I, for the same reason. When the purifiers have to be changed, the 

 vessel B is lifted up, until the bottom of the partition, at C in the elevation, 

 Fig. 25, clears the pipes, the outside rim remaining immersed in the tar (the 

 stops S on the guide-rods prevent it from being lifted too high), and turned 

 partly round until it occupies the position shown by the dotted lines in the 

 plan, Fig. 25 (2). The length of each dot N through which the guide-rods 

 M pass, mark this position and effectually prevent mistakes, for the vessel 

 cannot be turned the wrong way. 



K and L are the pipes connected with the second set of purifiers thrown 

 into action and into communication with F and I, when the vessel B is 

 shifted to the position shown by the dotted lines in the plan. 



P is a wooden frame supporting the pulleys and balance-weight Q to 

 assist in lifting the vessel B, which, while in action, is kept from rising with 

 the pressure of the gas by a bolt. 



In preparing the lime for the purifiers, it ought to be beaten, well sifted, 

 and water added, until, by compression in the hand, the lime will just adhere ; 

 if any lumps remain, their outside only will be acted upon ; when broken they 

 will be found untouched in the inside ; and although such lumps may be used 

 again, it is always better to systemize the process in the first instance, and 



