METALLURGY. 



487 



ior regenerating the electrolytes, with either 

 soluble or insoluble electrodes. The solution, 

 which contains most free acid, and which rises 

 to the top, flows over a wooden sill placed in 

 one corner of the zincking tank into an overflow 

 tank, from which it gravitates into a compressed- 

 air tank, when air is blown in and the solution 

 is forced up into the regenerating tanks. 



Wilder's patented process for coating steel and 

 iron consists in the use of a bath composed of 

 sine, tin, and aluminum. The mixture is claimed 

 to produce a coating on iron and steel much supe- 

 rior to any other known. It is so firmly adherent 

 that the sheets will stand working after it has 

 been applied, will resist corrosion, and can be 

 heated red hot without injury. The coating is 

 applied by the same method as galvanizing that 

 is, by dipping the cleansed sheets, etc., in the 

 melted alloy. 



In the Walrand-Legeneisel steel process the 

 castings may be made directly from the converter. 

 'The essential feature of the process is the addi- 

 tion of ferro-silicon containing from 10 to 12 

 per cent, of silicon to the charge in the con- 

 verter when the flame drop takes place, and then 

 making an after blow. The oxidation of the sili- 

 con generates a large amount of heat, which 

 is imparted to the metal, whereby it becomes 

 strongly superheated. The metal is very fluid, 

 castings made with it are free from blowholes, 

 and by the use of the process intricate castings 

 can be made down to a fraction of a pound in 

 weight. 



An acid-blast process for etching, by Mr. Louis 

 Edward Levy, consists essentially in the applica- 

 tion of a powerful blast of atomized acid or other 

 erodent in place of the customary immersion bath. 

 Along with the means of producing the requisite 

 blast of comminuted acid and applying it for the 

 purpose in view is combined an arrangement for 

 the necessary washing of the plate. The method, 

 while primarily intended to facilitate the etching 

 of photo-chemical-printing plates, is also appli- 

 cable in all cases where the chemical erosion of 

 metals or of glass is to be effected. 



In a method of coating wood electrically with 

 deposits of silver or copper, described by Mr. C. 

 F. Barnes, the wooden article is first saturated 

 with copper sulphate by immersing it in that 

 substance; it is then removed and thoroughly 

 dried. It is next exposed to the action of hydro- 

 gen-sulphide gas. This converts the sulphate of 

 copper to the sulphide, which is a conductor of 

 electricity and is insoluble in aqueous solutions. 

 The article is then wrapped with fine copper wire 

 and suspended in a solution of common salt at 

 the cathode, when a current is passed. The cop- 

 per sulphide is thereby speedily reduced by the 

 action of the cathode products to metallic cop- 

 per. When the reduction is supposed to be com- 

 pleted the article is transferred to an ordinary 

 copper-plating bath, where a coating of copper of 

 any desired thickness may be formed upon the 

 surface. For silver the process is modified by 

 immersing the object, after preliminary copper- 

 ing, in the silver-plating bath. 



Mr. Alexander Dick, who some time ago de- 

 vised a method and a machine for forcing metals 

 in 'a plastic condition through dies, has since 

 succeeded, after many experiments, in applying 

 his process to the making of tubes. The process 

 is also found very suitable for the production 

 of rods and sections of various lengths, and, 

 owing to the pressure under which the articles 

 are produced, they acquire, it is said, a homo- 

 geneity that can not be reached by other meth- 

 ods. An indication of the principle of the appli- 



cation of the process is given by the statement 

 that in the absence of atmospheric air and con- 

 sequent tendencies to oxidation copper and its 

 alloys are welded or reunited in such a manner 

 that the structure can not be distinguished from 

 casting. 



An electrolytic process for making parabolic 

 reflectors for search lights, described by Mr. 

 Sherard Cowper-Coles in the British Association, 

 consists in using a glass convex mold, on which 

 a coating of metallic silver is chemically de- 

 posited. This coating is then polished, so as to 

 insure the adherence of the copper backing to the 

 silver. The mold thus prepared is placed in a 

 suitable ring and frame and is immersed in an 

 electrolyte of copper sulphate, where it is rotated 

 in a horizontal position at the rate of about 15 

 revolutions per minute. The silver, with the 

 firmly adhering copper, which together form the 

 reflector, is subsequently separated from the glass 

 mold by placing the whole in cold or lukewarm 

 water and gradually raising the temperature of 

 the water to 120 F., when the unequal expansion 

 of the two substances causes a separation of the 

 metal from the glass mold. The concave surface 

 of the reflector obtained is an exact reproduc- 

 tion of the surface of the mold. It has the same 

 brilliant polish, and requires no further treat- 

 ment to answer all the purposes of a reflector, 

 except that it must be coated with a film of some 

 suitable metal to prevent its tarnishing. Pal- 

 ladium is found to answer this purpose best, as 

 a bright coating can be deposited rapidly to any 

 desired thickness. 



Apparatus. A paper read by Mr. A. P. Head 

 at the annual meeting of the English Iron and 

 Steel Institute described the tilting open-hearth 

 furnaces that are coming into use in the United 

 States as presenting a substantial advance in 

 metallurgy likely to have far-reaching effects in 

 the future of the Bessemer and open-hearth 

 processes. It is regarded as a link between the 

 Bessemer converter and the open-hearth furnace 

 in that it partakes in its construction of some 

 of the characteristics of both. The author, at 

 the meeting of the British Iron and Steel Insti- 

 tute, described two forms of this furnace and an 

 improved design. Among the advantages claimed 

 for the tilting over the fixed furnace are that the 

 slag can be poured off at intervals during the 

 melting process, and that as the pouring hole 

 of the furnace is above the level of the bath in 

 the normal position it is never closed up, but 

 only loosely covered to exclude the air. Conse- 

 quently the time taken to open the hole before 

 pouring and to repair and close it after pouring 

 is saved, as well as the labor connected therewith. 

 Further, since no injury is done to the pouring 

 hole by opening and closing, the life of the furnace 

 bottom is much prolonged. The cold air which 

 enters at the end ports when the furnace is tilted 

 is of advantage in that it chills the layer of slag 

 on the surface of metal, thereby effectually pre- 

 venting it from boiling and spurting. A consider- 

 able saving of metal is effected in the tilting fur- 

 nace by the fact that every particle of metal 

 and slag can be removed after each charge, while 

 in the fixed furnace small pools of metal lodge 

 in the inequalities of the bed and can not be re- 

 moved. Further advantages are that in it the 

 tapping of the charge can take place at the exact 

 moment when the metal is of the desired composi- 

 tion; that in case of any hitch or accident the 

 furnace can be instantly tilted back and the pour- 

 ing stopped; that it lends itself readily to the 

 transfer of metal from an acid to a basic furnace; 

 that the whole body of the furnace is easy of 



