COMPOSITION OF CHAMBER DUST. 



715 



in the state of cbloro bromo-ioditles aud sulphides formed by the action of cbloro- 

 broino-iodide of lead and silver, and of sulphide of lead in presence of carbon, on the 

 nonvolatile oxides. The volatile chlorides aud sulphides thus foriied are afterwards 

 decomposed by water, when the steam which accompanies the fumes condenses. These 

 I'eactious, which might appear doubtful from the examination of the chamber-dust 

 alone, are forcibly demonstrated by tlie analysis of that portion of the fumes which is 

 not condensed aud which escapes into the atmosphere. (See Analysi-i XXXVI.) 



Roasted dust — At One Smelter the flue and chamber dusts are roasted, previous 

 to resmelting, in the roasting furnace, which is spoken of in the description of this 

 smelter. This operation is probably carried on with a view to getting rid of the large 

 proportion of arsenic which is erroneously supposed to exist in the dust. Whatever 

 may have been the object of the superintendent of this smelter in performing this 

 costly operation, if the composition of the chamber-dust of this smelter is compara- 

 ble to that of the others, the influence of roasting on chamber-dust can be easily seen 

 by comparing Analysis XXXV of the roasted dust with Analyses XXXIII aud 

 XXXIV. 



The sample analyzed in XXXV is chiefly formed of roasted dust, but it contains 

 also a little unroasted dust, which had been spread over the roasted dust taken out of 

 the roasting furnace. The specimens mixed for analysis were in friable whitish and 

 reddish mas.ses, containing scarcely any charcoal or coke dust. The elementaiy anal- 

 ysis was made like those of the chamber-dust, and the diflerent portions analyzed are 

 in the following propoi'tions : 



Portion soluble iu -svater 1. Ifi588 



Portion soluble iu acids... 85.48129 



Portion insoluble in acids 13. 29600 



Loss 0.05683 



Total 100.00000 



Analysis XXXV. Roasted chamber dust. 



ElemenUirj/. 



Lead 63.130100 



Silver 0.112000 



Gold 0.000200 



Bismuth 0. 05U20 



Zinc ' 1.479920 



Cadmium 0.004800 



Iron 8.891900 



Manganese 0.551270 



Copper 0.115600 



Arsenic 0.210000 



Antimony 0.092940 



Tin 0.003478 



Soda 0.015000 



Hygroscopic water 225000 



Sulphuric acid 10.929000 



Phosphoric acid 0.319800 



Carbonic acid Trace 



Titanic acid 0.055800 



Silica (from slag and silicate of lead) 8. 332000 



Silica (from quartz and refractory silicates) 1. 50C000 



Oxygen 



Selenium and tellurium 



Sulphur 



Chlorine 



Potassium 



Sodium 



Alumina 



Lime 



Magnesia 



Potash 



Bromine 



Iodine 



Carbon (from charcoal and coke) 



Graphite 



Indium, thallium, new metal 



Loss 



Total 



Silver ounces to ton. 



Gold do... 



8. 242172 

 Traces 

 0. 490000 

 0. 694840 

 0. 054590 

 0. 051300 

 1. 144400 

 0. 700240 

 0. 512200 

 0. 025000 

 0. 142420 



0. 007780 



1. 505000 

 0. 290000 



Traces 

 0. 05083C 



32. 600 

 0. 053332 



