230 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
As regards the extraction of zinc from its ores, the Hoepfner pro- 
cess is in operation at Winnington in Cheshire and at Hruschau in 
Austria. By this process, zinc chloride is obtained from the waste 
liquors of the ammonia-soda process, and is electrolyzed in order to 
obtain metallic zine and chlorine gas. 
A zinc-ore chlorination process, patented by Swinburne and Ash- 
croft, is operated at Weston Point, England, by the Castner Kellner 
Alkali Company. Zinc-sulphide ores are treated with hot chlorine 
gas, and the corresponding chlorides are obtained, but the zine chlo- 
ride is sold as such, and is not subjected to electrolysis as described in 
the patents covering this process. 
Electro-thermal methods of treating raw zine and zinc ores are 
being experimented with by de Lavel and by Ferraris, in Sweden and 
Italy. The de Lavel furnace has already produced some hundreds of 
tons of pure zinc from spelter, but I understand that it has not yet 
been applied with success to the reduction of the ore. At Monte- 
Poni in Italy, Ferraris is carying out similar trials with an electric 
furnace, and has estimated the cost of the process at 40 lire per ton 
of calamine. In a recent letter he stated, however, that the method 
has not yet reached the industrial stage of its development. 
