METALLURGY. 



4G9 





oxidation, sulphurization, and addition of galena, 

 the residuary lead may be rendered very rich in 

 silver. 



The high grade lead ores (galenite) of south- 

 west Missouri and southeast Kansas are treated 

 at the Joplin Works in a special manner so as to 

 produce partly metallic lead and partly a white 

 pigment, " sublimed white lead." The ore, being 

 treated in a modified Scotch hearth, produces pig 

 lead and a rich lead slag, and lead fumes, which 

 are thoroughly condensed. The slag and fumes, 

 with a quantity of second-grade ore. are treated 

 by the Lewis-Bartlett process. The vapors are 

 oxidized and form a pigment sublimed white 

 lead which consists mainly of an % amorphous 

 sulphate and oxide of lead, incidentally contain- 

 ing a small percentage of oxide of zinc. It is a 

 good basis for a paint, and is used in the manu- 

 facture of rubber goods. 



The F. L. Bartlett zinc-lead process, used at 

 Canon City, Colorado, for the treatment of ar- 

 gentiferous zinc-lead sulphite ores, consists, in 

 general, in separating the zinc and lead by vola- 

 tilizing them in the form of a zinc-lead fume, 

 from which a marketable pigment is obtained, 

 while the silver is left behind with the other non- 

 volatile metals, and is collected in a copper matte. 



The trials of the system of producing zinc elec- 

 troly tic-ally which have taken place at the works 

 of the Sifesian Company prove, it is said, the 

 practicability of the method, but do not show, 

 on the whole, that the process is superior to the 

 old one. 



Three different processes have been invented 

 by C. A. J. II. and II. E. R. Schroeder for recov- 

 ering the zinc from used-up galvanic battery so- 

 lutions. In the first arrangement a concentrated 

 solution of sodic carbonate is added to the zinc 

 solution, and the precipitate, consisting of zinc 

 carbonate, is separated by decantation. The zinc 

 carbonate is then dried, and is treated by a usual 

 process, to extract the metallic zinc. In the sec- 

 ond process, sodic sulphate (a by-product in the 

 manufacture of nitric acid) is employed. It is 

 dried, mixed with chalk, and converted into 

 sodic carbonate, with which the zinc solution is 

 precipitated. Sodic sulphate is also employed in 

 the third process, which further includes the 

 recovery of sulphuric acid. The sulphate is 

 dried, mixed with peroxide of iron or iron and 

 coal, and melted. The melted mass is drawn out 

 into molds, and when cool the blocks are exposed 

 to the action of air or carbon-dioxide gas, under 

 which they fall into a powder. This is dissolved 

 in water, and the clear solution is used for pre- 

 cipitating the zinc. The sulphuric acid is sepa- 

 rated from the residue by a special process. 



In smelting zinc at the'Bertha Works, Virginia, 

 the calamine ore, having been calcined to expel 

 its combined water and mixed with the proper 

 proportion of anthracite coal, is charged into the 

 retorts, which are made of selected fire clay, and 

 a short clay condenser is set in the mouth of each 

 retort and luted with clay. The furnace is then 

 fired from below, the flames circulate around and 

 between the pots, and the zinc ore is reduced by 

 the combination of the carbon of the coal with 

 the oxygen of the ore. At first a bright blue flame 

 burns at the mouth of each condenser, but when 

 the furnace charge reaches a bright-red heat, 

 metallic zinc is volatilized and burns at the 



mouth of the condenser with a brilliant greenish- 

 white flame. Conical iron pipes are then placed 

 over the condensers in order to assist the con- 

 densation of the metal, which deposits inside the 

 pipe in the form of metallic zinc. At stated in- 

 tervals the pipes are removed and the molten 

 metal is scraped out of the condensers into ladles, 

 from which it is poured into molds to form the 

 slabs of commercial spelter. This is continued 

 till the furnace has been worked off and all the 

 metal extracted from the ore. Eighty per cent, 

 of the metallic contents of the ore is usually ob- 

 tained ; the remaining 20 per cent, is lost by vola- 

 tilization or absorbed in the retorts, or left in the 

 residue. As metallic zinc has a strong affinity 

 for iron, no iron tool or vessel is allowed to come 

 in contact with the zinc in its molten condition. 



Alloys. During the last few years alloys of 

 tin and lead have been employed in manufac- 

 tures in which the constancy of melting points 

 after successive meltings played an important 

 part. Rudberg, one of the earliest workers in 

 this field, noticed that the thermometer stopped 

 at two points during the solidification of these 

 alloys. The higher point varied with their com- 

 position, while the lower point was constant, and 

 was identical with the melting point of the 

 " chemical alloy " represented by the formula 

 PbSna. Recently the results have been given 

 by Wiesengrund of a complete series of experi- 

 ments with tin-lead alloys ranging from PbSn 12 

 to Pbi 2 Sn. In density the alloys were all lighter 

 than might have been expected from the densi- 

 ties of their constituents. The increase of vol- 

 ume was greatest in the case of the " chemical 

 alloy " PbSn s , and decreased as one or the other- 

 constituent predominated. The process of solidi- 

 fication showed Rudberg's two points distinctly. 

 The higher one, called the melting point, was 

 really a point at which the cooling became some- 

 what less rapid. The lower, called the point of 

 solidification, was truly a stationary point, ex- 

 cept in the alloys containing much lead. A 

 plausible explanation of the phenomena is given 

 analogous to the theory of saline solutions, tin 

 being regarded as the solvent. 



Numerous valuable qualities are claimed for 

 the aluminum alloy silvinite, which has now 

 been put upon the market at merchantable prices. 

 It can be beaten out thin as gold leaf, and has 

 an appearance comparable with that of silver. 

 For surgical purposes it will be useful, as it is 

 not acted upon by organic secretions. Its non- 

 corrosive properties give it preference for the 

 manufacture of articles in which acids act dele- 

 teriously upon ordinary metals. The metal 

 "enamels" and "takes" oil colors beautifully, 

 and sheets and plaques are being made of it in 

 large quantities for artists. For military pur- 

 poses it will command considerable attention. 

 The addition of a small percentage of it to type 

 metal adds to the durability of the same. Steel 

 and other castings attain a greater degree of 

 fluidity by an admixture of silvinite. A very 

 beautiful alloy is produced by mixing 25 parts 

 of silvinite to '75 parts of gold, a rich tint being 

 the result. The new alloy is excellent for all 

 uses in which great sonority is required. It 

 is proof against moisture and sea water, and 

 hence is suitable for sheathing vessels. Mixed 

 with a small percentage of silver, it is consider- 



