304 MmmG iinDUSTRY. 



ing oiF the refined metal. At the base of tlie stack is a chamber for the col- 

 lection of the oxidized antimony that may condense in the stack and fall to 

 the bottom. The whole structure is firmly bound together by irons and bolts, 

 as shown in the drawings. In the figures, G is the fireplace ; H, the ash pit ; 

 /, the bridge ; J, the air-channel through the bridge ; K^ the pan ; X, the 

 spout ; . M, the openings for putting in and working the charge ; N, the 

 doors ; O, the chamber at base of stack for the accumulation of the oxidized 

 antimony. 



To set this furnace in operation the metal may be first melted and intro- 

 duced in a fused state to the pan ; or, what is more common, the pan is 

 heated to redness and the pigs of crude metal are laid upon the pan-bottom, 

 when melting ensues. The fire may be quite moderate, the only fuel used 

 in this case being sage brush. The antimony is oxidized and passes up the 

 stack, a part to escape, a part condensing in the chimney. The charge of 

 the pan at the outset is some six or eight tons, but as the molten metal, 

 diminishes in bulk by the sublimation of the antimony, new bars are added 

 to keep up the supj^ly. A scum collects on the surface of the molten metal 

 which is removed by scrapers from time to time. This consists chiefly of 

 lead and antimony with very little silver. While this refining process was 

 still practiced at the works, these skimmings were collected, re-melted, and 

 cast in bars, to be sold in San Francisco for type-metal. Babbitt-metal and 

 other purposes. The alloy consisted of 71 per cent, of antimony with 2.9 

 per cent, of lead and was worth 8 cents per pound. 



The lead in the pan is gradually enriched by this method of concen- 

 tration, and assays are taken from time to time, usually at intervals of twelve 

 hours, for the purpose of watching the progress of the operation. When the 

 value of the lead has been brought up to about $350 or $400 per ton, it is 

 drawn ofi" in molds and then subjected to treatment in the cupel-furnace. 



The following series of assays, taken during the progress of one run of 

 metal shows the gradual improvement of the lead: 



March 10, raw metal at time of charge, value per ton $209 68 



10, twelve hours later, value, per ton, of contents of bath 214 04 



11 do do do 219 44 



II.--. do do do 238 93 



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