SMOKE AND DUST ABATEMENT COTTRELL. 659 



proved nearlj-, if not quite, as hard to get rid of, and as objectionable 

 to the neighbors, as the smelter fumes themselves; and many suits 

 have been brought against the plants for pollution of streams and 

 other nuisances due to these liquors. So, after all, this would simply 

 mean displacing a nuisance from one industry by extending that 

 from another, although in the end it may prove merely a step in 

 the solving of both problems. 



As already stated, many proposals have been made to simply dis- 

 solve and wash away the gas in solution, but, while in the pure state it 

 is fairly soluble in cold water, its dilution in average smelter gases 

 and the high temperature of the latter make this mode of collection 

 very difficult on the large scale and even if carried out it would leave 

 a veritable ocean of dilute acid liquors which might easily prove more 

 dangerous to the surrounding country and harder to get rid of than 

 the original gases. The neutralization of this liquor with lime has 

 been suggested and, in fact, this procedure actually obtains at the 

 Ashio smelter in Japan,^ where specially favorable conditions seem 

 to exist, but, as the weight of lime required in some of our smelters 

 would be over half that of the ore, this, too, is only applicable in 

 very special cases. 



Another ingenious suggestion has been to moisten the finely ground 

 slag from the smelter itself, and use the metallic bases therein con- 

 tained as chemical absorbents for the gas, at the same time unlocking 

 and recovering in solution such of the valuable inetals as this slag still 

 contains.- Up to the present, however, this method has not proved 

 commercially successful, on account of the slowness of the reaction, 

 but its fundamental idea of combining the two great waste products 

 from the smelter for the purpose of further mutual beneficiation of 

 both is certainly an attractive one. Although it does not appear as 

 necessarily hopeless, the difficulties and uncertainties in the way of its 

 practical application are still certainly very great. 



Last but not least is the possible alternative of reducing the sulphur 

 dioxide back to solid sulphur, or, better still, so smelting the ore in 

 the first place that as much of the sulphur as ]30ssible is given off and 

 collected as such instead of being burnt to its gaseous oxide as at 

 present. Both of these methods for obtaining the sulphur in the free 

 state are now attracting the serious attention of metallurgists. 



The earliest experiment, both in the laboratory and on a practical 

 scale, dates back many years,^ but recently the subject has again come 



1 The Japan Excursion of the American Institute of Mining Engineers, Jos. W. Richards, 

 Met. and Chem. Engineering, vol. 10, p. 20-21, Jan., 1912. 



2 The Westby-S5rensen Process, by E. P. Jennings, Eng. and Mln. Journ., vol. 86, pp. 

 418-419, Aug. 29, 1908 ; also U. S. Pat. 875222, Dec. 31, 1907. 



3 Aeltere und Neuere Verfahren zur Unschiidlichmachuug des Hiitteurauches durch 

 Abscheidung des Schwefels aus seinen Oxydationsprodukten, by Otto Vogel, Ranch und 

 Stuub, a. 68-71, December, 1912; also Handbook of Metallurgy, by Carl Schnabel, trans- 

 lated by Henry Louis, 2d edition, 1907, vol, 2, pp. 69-76. 



