386 



METALLURGY. (ALUMINUM.) 



per bottoms, which being granulated, oxidized, 

 and resmelted with sulfur-bearing material, gave 

 a second bottom very much richer than the first. 

 The presence of some lead is essential to obtain- 

 ing a perfect concentration. Six parts of lead 

 to one of copper give satisfactory results; but 

 the bottom from the second selecting was so 

 rich in lead that it could be expelled, often di- 

 rectly, without any addition of that substance. 

 The first bottoms could be resmelted directly 

 with sulfur-bearing material without granula- 

 ting and oxidizing; and the operation could be 

 repeated until the concentration had reached the 

 desired degree. The author also found this meth- 

 od satisfactory in smelting Cripple Creek ores in 

 Colorado. 



Platinum is a metal of great value to the 

 chemist and the artisan on account of its melt- 

 ing only at an extremely high temperature and 

 its resistance to the action of all acids except the 

 nitrohydrochloric. It is largely used in chemical 

 processes, in the forms of crucibles, dishes, 

 spoons, spatulas, foil, and wire. Its coefficient 

 of expansion being nearly the same as that of 

 glass, it has been largely employed in the con- 

 struction of incandescent electric lamps for con- 

 necting the outside copper wire with the carbon 

 filament. It is used in the manufacture of the 

 contact points of telegraph-keys, in the pins for 

 attaching artificial teeth to the plate, in stills 

 for the concentration of crude sulfuric acid, 

 when it is alloyed with about 3 per cent, of 

 iridium; to some extent in jewelry; in the manu- 

 facture of platinotype paper for printing photo- 

 graphs; in the construction of fine weights for 

 chemists' balances, for surgical and other scien- 

 tific instruments, for making balance-wheels and 

 hair-springs of non-magnetic watches, for obtain- 

 ing a silver color on porcelain, for producing what 

 is called " oxidized silver," and for the fuses of 

 electrically exploding dynamite cartridges. Al- 

 though platinum has been supposed for many 

 years to exist in New South Wales, its actual 

 discovery there in paying quantities dates only 

 from 1893. The amounts at present obtained are 

 limited, the chief difficulty in the way of pro- 

 duction being the scarcity of water in the dis- 

 tricts where it occurs. It is found in the native 

 state alloyed with iron, iridium, osmium, and 

 other rare metals. It usually occurs in grains 

 or scales, sometimes in irregular lumps or nug- 

 gets, and rarely in crystals. In the Fifield dis- 

 trict, about 322 miles west of Sydney, it is asso- 

 ciated with gold, the metals occurring in fairly 

 coarse water-worn grains, confined as a rule to 

 the cavities of the bed-rock, and to the wash-dirt 

 for a few inches above it. As compact platinum 

 does not amalgamate with mercury in the cold, 

 it can easily be separated from gold by means 

 of that agent. Platinum is also found in the 

 beaches of the northern coast of the state of New 

 South Wales, where it is obtained from the aurif- 

 erous sands. Here the gold, platinum, etc., which 

 are concentrated on the beaches during stormy 

 weather are brought down by the action of the 

 waves from an ancient beach deposit which oc- 

 curs at an elevation of about 6 feet, and which 

 has locally received the name of " black rock." 

 The only other form than those mentioned above 

 in which platinum is found is that of an arsenide, 

 in the mineral sperrylite, which occurs in minute 

 cubic or cubo-octohedral crystals having a tin- 

 white color and a black streak. 



Tn the treatment of cinnabar ores at the works 

 of the Marfa and Mariposa Mining Company, 

 Brewster County, Texas, as described by E. B. 

 Spalding, the crushed ore is charged hourly by a 



car holding 900 pounds, and every half-hour half 

 a car of spent ore is withdrawn below. It takes 

 the ore about twenty-four hours to pass through 

 the furnace. The fumes leaving the furnace by 

 a 16-inch sheet-iron pipe, zigzag through con- 

 densers, each with a partition wall before they 

 pass through a long flue into the air. The con- 

 densers are dry on account of the scarcity of 

 water. Most of the quicksilver collects in the 

 first three chambers, which are freed from soot 

 weekly, while the other three have to be cleaned 

 only once a month. The condensed quicksilver 

 runs off continuously into a storage-tank to be 

 bottled. The soot is freed from a large part of 

 its quicksilver by working on an inclined plane, 

 where it is added in small amounts to the ore 

 charge. The yield in quicksilver is estimated to 

 be 90 per cent. In five months 1,200 flasks of 

 quicksilver were produced. 



Aluminum. A purity is said by W. Murray 

 Morrison to be attained now in electrolytic alu- 

 minum of 99.5 and 99.6 per cent., the impurities 

 being 0.25 per cent, of iron and 0.17 per cent, of sili- 

 con. Another example analyzed by Prof. E. Wil- 

 son gave 0.31 per cent, of iron and 0.14 per cent, 

 of silicon. Such a standard of purity has been only 

 gradually obtained. The importance of purity is 

 insisted upon by the author in his paper in the 

 Journal of the Institute of Electrical Engineers, 

 since impurity affects the value of the metal as an 

 electric conductor in two ways: by lowering the 

 conductivity and by increasing the liability to 

 atmospheric corrosion. The evidence is some- 

 what conflicting as to the power of aluminum 

 to withstand atmospheric influences; but on the 

 whole the metal seems fairly satisfactory in this 

 respect. The thin film of oxid which imme- 

 diately forms on its surface in air acts as a 

 protective coating. The usefulness of aluminum 

 in metallurgy, of w r hich much has already been 

 said in previous volumes of the Annual Cyclo- 

 paedia, is continually becoming more apparent 

 and better appreciated. Of the part it plays in 

 this field, Mr. Morrison speaks of the improve- 

 ment secured to the finished product through the 

 addition of a small quantity of aluminum (from 

 2 to 5 pounds per ton) in the casting of steel, iron, 

 brass, and other metals, when the aluminum 

 combines with the occluded gases, with the effect 

 of reducing the blow-holes and rendering the 

 metal which is being cast more fluid and ulti- 

 mately more homogeneous. Much is expected 

 from the application of Dr. Goldschmidt's use of 

 aluminum for producing high temperatures to 

 the welding of rails, pipes, etc. (noticed in the 

 Annual Cyclopaedia for 1901), which has not yet 

 become of commercial importance. By virtue of 

 the low specific gravity of aluminum it is used 

 in cases in which weight is a drawback in naval 

 and military equipments, motor-car construction, 

 and like applications in which the metal finds 

 considerable and increasing employment. For 

 cooking utensils, for which it is eminently suited, 

 ils use is steadily increasing. The chief draw- 

 back to the general use of aluminum is its low 

 tensile strength. This may be improved to some 

 extent by alloying with a small quantity less 

 than 10 per cent. of nickel or copper. A table 

 has boon prepared by Prof. Wilson incorporating 

 data with reference to some of these light alloys. 

 Substituted for copper in electric conductors 

 aluminum allows wider spans; but when insu- 

 lated cables are wanted for low-tension work, 

 the increased diameter of aluminum conductors 

 involves increased cost in insulating material. 

 In lead-covered cables, the increased weight of 

 lead would almost, if not quite cancel the de- 





