4.54 Sir Henry Koscoe [May o, 



mencing the operation, these covers are raised in the heated furnace 

 through apertures provided in the floor of the heated chamber, and are 

 then fastened in their place by an attachment adjusted to the stem ; the 

 hollow arm extends outside the furnace. Directly below each aperture 

 in the bottom of the furnace are situated the hydraulic lifts ; attached 

 to the top of which are the platforms upon which are placed the 

 crucibles to be raised into the furnace. Attached to the hydraulic 

 lifts are the usual reversing valves for lowering or raising, and the 

 platform is of such a size as, when raised, completely to fill the 

 bottom aperture of the furnace. The charged crucible, being placed 

 upon the platform, is raised into its position, the edges meeting those 

 of the cover, forming an aii*-tight joint which prevents the escape of gas 

 and vapour from the vessel during reduction, except by the hollow arm 

 provided for this purpose. The natural expansion of the iron vessels 

 is accommodated by the water-pressure in the hydraulic lifts, so that 

 the joint of the cover and crucible are not disturbed until it is intended 

 to lower the lift for the purpose of removing the crucible. 



The length of time required for the first operation of reduction 

 and distillation is about two hours. At the end of this time the 

 crucibles are lowered, taken from the platforms by a large pair of 

 tongs on wheels, carried to a dumping pit, and thrown on their 

 side. The residue is cleaned out, and the hot pot, being again 

 gripped by the tongs, is taken back to the furnace. On its way, the 

 charge of alkali and reducing material is thrown in. It is again 

 placed on the lift and raised in position against the edges of the 

 cover. The time consumed in making the change is IJ minute, 

 and it only requires about seven minutes to draw, empty, recharge, 

 and replace the five crucibles in each furnace. In this manner the 

 crucibles retain the greater amount of their heat, so that the operation 

 of reduction and distillation now only requires one hour and ten 

 minutes. Each of the four furnaces, of five crucibles each, when in 

 operation, are drawn alternately, so that the process is carried on night 

 and day. 



Attached to the protruding hollow arm from the cover are the 

 condensers, which are of a peculiar pattern specially adapted to this 

 process, being quite different from those formerly used. They are 

 about 5 inches in diameter, and nearly 3 feet long, and have a small 

 opening in the bottom about 20 inches from the nozzle. The bottom 

 of these condensers is so inclined that the metal condensed from the 

 vapour issuing from the crucible during reduction, flows down and 

 out into a small pot placed directly below this opening. The 

 uncondensed gases escape from the condenser at the further end, and 

 burn with the characteristic sodium flame. The condensers are also 

 provided with a small hinged door at the further end, by means of 

 which the workmen from time to time may look in to observe how 

 the distillation is progressing. Previous to drawing the crucibles 

 from the furnace for the purpose of emptying and recharging, the 

 Bmall pots each containing the distilled metal are removed, and empty 



