434 



METALLURGY. 



running \vero poor in cubic crystals of the com- 

 pound SbSn. Babbit's metal i's made amorphous 

 by casting in cold molds. Axles running on such 

 metal get tinned ; this leads to sticking and heat- 

 ing; finally recrystallization sets in, and liquid tin 

 is squeezed out, while a compact layer of crystals is 

 formed on the axle. Microscopical" examination of 

 tin- metallic deposit from the lubricating oil led to 

 the unexpected result that metal with crystals of 

 moderate size will develop ball cushions. Tin is 

 ground to a fine dust by the sharp fragments of 

 the bronze needles, the hard cubes of SbSn are 

 rounded, undermined, and finally worked up into 

 something like metallic pebbles of microscopical 

 size. Similar spheroids were obtained from bear- 

 ings of magnesia metal and of aluminum brass, but 

 not from ordinary brass nor from gray cast iron. 



Medals of bronze, Prof. Roberts-Austin says, 

 differ considerably from those of silver, in that 

 their surfaces are far more liable to be affected by 

 the slow operation of atmospheric influences and 

 by the more rapid action of chemical agents. An- 

 cient silver coins, for instance, which have been 

 long buried in the earth, do not show anything 

 like so wide a range of color in their patina or crust 

 as is revealed on coins of brass, bronze, or copper 

 which have been hidden in the same way. This is 

 due to the fact that silver is much less affected 

 than copper by the chemical action of the constitu- 

 ents of soils, cr by atmospheric influences. The 

 rust of a patina which is formed, a skin or pellicle 

 of oxide, serves to protect the surface of the medal 

 from further changes. In modern times most 

 UK dais to which the name of bronze is given are 

 really of copper, " bronzed " or colored artificially on 

 the surface. The process consists in applying with 

 a brush a composition of common crocus powder 

 and jeweler's rust, and polishing when dry and 

 cold. A composition of verdigris, 87 grains ; sul- 

 phate of copper. 437 grains : niter, 87 grains; com- 

 mon salt, 68 grains; sulphur, 233 grains; and water, 

 1 gallon, has also been found to answer fairly well. 

 A Japanese " verdigris " called " rokusho " maybe 

 made by slight variations in its composition to 

 give copper a great variety of tints, ranging from 

 golden yellow through deep brown to bright red. 

 The quality of the copper also exerts a very great 

 influence on the tint of the patina. In France 

 medals of true bronze containing much zinc are 

 struck, and although the color is heightened by 

 superficial oxidation, produced by gentle heating, 

 no true patination is effected. 



A metallic preparation for plating iron and steel, 

 patented by W. J. Wilder, consists of an alloy of 

 zinc, tin, and aluminum, and is claimed by the 

 inventor to possess superior qualities. It becomes 

 alloyed to the base, and is so thoroughly attached 

 that the sheets, for example, will stand working 

 after the coating has been applied, will resist corro- 

 sion, and can be heated red hot without injury. 



Processes. In the Cowper-Coles electrolytic 

 cyclic process for the treatment of refractory ores, a 

 special feature of interest is the throwing down of 

 the zinc from the sulphate solution upon aluminum 

 plates, which can be either stationary or caused to 

 revolve. The use of aluminum, through the forma- 

 tion of a loose film of oxide, greatly facilitates the 

 stripping of the zino from the cathodes. Zinc 

 sponge deposited on the revolving disks is scraped 

 off by means of adjustable wood scrapers, and al- 

 lowed to gravitate into a receiving box, where it is 

 drained. It is then dried, and forms a good sub- 

 stitute for what is commonly known as zinc dust, 

 the gravish amorphous substance obtained as a 

 sublimul product during the (list illation of zinc 

 from its ores. This zinc dust is largely used in the 

 Cowper-Colea regenerative electro-zincing process. 



The lead obtained by leaching out with a solution 

 of caustic soda is also deposited on revolving disks, 

 and the deposit is scraped off from time to time. 

 Litharge is made from the sodium plumbate solu- 

 tion by evaporating it at a temperature not exceed- 

 ing 80 C. 



A recent process for metallizing wood consists in 

 first immersing the wood for three or four days in 

 a caustic alkaline lye, and passing it thence imme- 

 diately into a bath of hydrosulphite of calcium, to 

 which is added, after twenty-four or thirty-six 

 hours, a concentrated solution of sulphur in caustic 

 potash. The bath has a temperature of from 50 

 to 55, and the wood is immersed in it for forty- 

 eight hours. Finally the wood is immersed for thirty 

 or forty hours in a hot solution of acetate of lead. 

 It is represented that wood prepared in this man- 

 ner, and after having undergone, a proper drying at 

 a moderate temperature, acquires under a burnisher 

 of hard wood a polished surface and exhibits a very 

 brilliant metallic luster. The luster is further in- 

 creased if the surface of the wood is rubbed, in the 

 first place, with a piece of lead, tin, or zinc, and 

 afterward polished with a glass or porcelain bur- 

 nisher. 



A process for the electrolytic manufacture of 

 white lead consists in the action of electrolytic-ally 

 generated nitric acid on lead. Of the four reactions 

 in the process, the first consists in the electrolytic 

 preparation of nitric acid and sodium hydroxide ; 

 the second in the formation of lead nitrate by the 

 action of the nitric acid on the lead. Then lead 

 hydroxide is formed by the reaction of lead nitrate 

 and sodium hydroxide ; and, finally, the combina- 

 tion of lead hydroxide and sodium bicarbonate 

 forms a lead carbonate or white lead. 



Utilization of the very high temperature (3,000 C.) 

 produced by the union of aluminum with oxygen 

 for soldering purposes, or for the preparation of 

 pure metals and alloys, is suggested by Mr. Gold- 

 schmidt in the " Zeitschrift fur Elektroclietnie." 

 When a more moderate temperature is sufficient 

 for the work to be done, the active mass may be 

 diluted by the addition of some inert substance a 

 metallic oxide, iron ore, silica, etc. Soldcrings 

 effected with heat from such a source are con- 

 sidered better than electric solderings because of 

 the greater uniformity of the temperature. The 

 author showed the German Elektrochcmical Society 

 a large mass of chromium which had been prepared 

 by treating a mass of oxide of chromium and pow- 

 dered aluminum in a crucible which was provided 

 with a covering of magnesia. The reaction \v;is 

 started by burning a little magnesia, after which the 

 mixture was added till the crucible was full. A I't cr 

 cooling the crucible was broken and the ingot of 

 chromium was taken out. By making two holes in 

 the crucible, one for the introduction of the mixture 

 and the other for the outflow of the chromium, we 

 can have a continuous process, as in the electric 

 furnace. The temperature obtained is higher than 

 in the ordinary electric furnace. The aluminum 

 produced may be converted anew into aluminum 

 which can be used again, or it may bo employed 

 for polishing, for which it has some advantage-- 

 over emery. Most of the metals can be reduced 

 ,from their oxides and various alloys can be pre- 

 pared by this method. The furnace residue con- 

 tains little rubies colored by chromium. To pre- 

 pare the pure metals it is necessary to use pure 

 aluminum; but when a high temperature only is 

 wanted crude aluminum will do. 



In experiments in the application of pressure t> 

 filings of iron, steel, copper, tin, etc.. Profs. Adams 

 and Nicholson, of McGill University, have found 

 that by the use of a compressor capable of applying 

 78,000 pounds to the square inch, metallic filings or 



