COMPOSITION OF FUMES LOST IN AIK. 



717 



dicates that roasting chamber-dust in Leadville is a useless and a ruinous operation, 

 by which nothing is gained and by which many valuable substances, lead, silver, fuel, 

 etc., are lost, at great expense. It is only fair to state once more that roasting of 

 chamber dust has only been done at one smelter. The analyses show that the mis- 

 chievous substances of chamber-dust are not arsenic and antimony, but chlorine, 

 bromine, iodine, and phosphoric acid. Analysis XXXVI, of the portion of lead fumes 

 lost in the atmosphere, will further demonstrate this statement. A priori, the best 

 way of treating lead dust and fumes is to resmelt them with an excess of lime, in 

 order to fix the volatile constituents by combination with calcium and lime. This is 

 precisely what is done in practice at most of the smelters, the only improvement that 

 might be suggested being the use of pure lime instead of the maguesiau lime of Lead- 

 ville ; but the writer thinks the general use of caustic lime instead of limestone would 

 be of great advantage to smelting at Leadville, since the chloro-bromo-iodo phosphates 

 of lead are driven off in the state of fumes in the furnace, before limestone, by the loss 

 of carbonic acid, has become caustic and thus acquired the power of acting chemically 

 on the fumes with which it comes in contact. 



Lead lost in fumes. At the time the writer was collecting notes and specimens for 

 this report, it happened fortunately that experiments were being made with the Bart- 

 lett smoke-filter (described on page 073), at the Grant smelter, for the purpose of con- 

 densing that portion of the lead fumes which' escapes with the smoke into the atmos- 

 phere. A fine opportunity was thus had of making a thorough investigation of that 

 part of the smelting products which is always lost at all the smelters. The analysis 

 of these fumes proves to be the most interesting by far of all those made on lead dusts, 

 since they are not only richer in lead than any of the others and contain more silver 

 than the average Leadville slag, but they show also other remarkable peculiarities, as 

 an inspection of the following analysis will show. They have exactly the appearance 

 of soot or lampblack. 



ANALYSIS XXXVI. FUMES FROM BARTLETT FILTER. 

 Elemintary. 



a The soot contains also a trace of graphite. 



