COMPOSITION OF FUMES LOST IN AIK. 



717 



dicates that roasting cbaiuber-dust iu Leadville is a useless aud a ruiuous opeiatiou 

 by wliicb uotbiiig is gaiued aud by which niauy valuable substauces, lead, silver, fuel, 

 etc., are lost, at great expeuse. It is ouly fair to state ouce more that roastiug of 

 chamber dust has only been doue at oue soielter. The analyses show that the mis- 

 chievous substauces of chamber-dust are uot arsenic aud antimony, but chloriue, 

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

 lost in the atmosphere, will further demoustrate this statemeut. A priori, the best 

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

 order to fix the volatile constituents by combiuation with calcium aud lime. This is 

 precisely what is doue iu practice at most of the smelters, the only improvemeut that 

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

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

 be of great advantage to smeltiug at Leadville, siuce the chloro-bromo-iodo phosphates 

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

 of carbonic acid, has become caustic aud thus acquired the power of actiug chemically 

 on the fumes with which it comes in contact. 



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

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

 lett smoke-filter (described on page G73), at the Grant smelter, for the puriiose of con- 

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

 phere. A fine opportunity was thus had of making a thorough investigatiou 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 iu lead than any of the others aud contain more silver 

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

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

 of soot or lampblack. 



Analysis XXXVI. Fuimes fhom Bahtlett filtek. 

 Elennntarij. 



a The soot contains also a trace of graphite. 



