Trials made at the Mansfield Copper Works have proved that an addition of 0*45 per cent. of manganese-copper is sufficient to toughen copper, which only retains 0.005 to 0.022 per cent., while the greater portion, after having taken away the absorbed oxygen, is carried off in the refinery slag. Manganese-copper has also a beneficial influence upon the toughness and density of thin copper castings, such as thin sheets, tubes, kettles, cauldrons, and other kitchen utensils, which formerly were beaten or pressed into shape; copper cast with an addition of the alloy shows itself extremely tenacious, and tubes of 1 1/3 in. diameter and only 0.07 in. thickness will stand a pressure of over 1100 lb. per sq. in., when water begins to be pressed through the pores of the metal. It appears that " cast copper," which can be brought in any required shape without the necessity of soldering, beating, hammering, pressing, or drawing, will in future play a considerable part in the arts and manufactures.
Some samples of black copper oxide and pig copper from Colorado were sent to Egleston to examine for arsenic and antimony, but he found none present. A quantity of this material was purchased by a large metallurgical works, and when they attempted to refine it, they pronounced it to be full of arsenic and antimony; so much so, that their furnaces were, as they said, " poisoned," and rendered unfit for refining. He then re-examined the samples, and at the same time some of the material which had "poisoned" the furnaces, and found no traces of arsenic or antimony when the usual amounts for analysis were used; but on taking very large amounts, he found traces merely in some parts of the sample, but not in all. As it was a matter of interest to ascertain what the white substance that " poisoned " the furnace was, he sent to the works making the black copper, and obtained some of the matte from which the black copper was made. He then found the impurity to be tellurium, a substance not heretofore known as occurring in copper.
He gives the following analyses of the matte, and of the black and refined copper:-
Copper . .
Gold . .
Silver . .
Zinc and ] Nickel ]
Iron . .
Arsenic • •
The mattes and the black copper are results of the treatment of copper ores with the tellurium ores of Colorado. In the laboratory no traces of white fumes were shown on charcoal; but when the metal in the furnace was subjected to the process of "dry roasting," as was unintentionally done, very dense white fumes were given off. When refined and cast into cake, it had the ordinary appearance of cake copper. At the first pass in the rolls, very fine cracks showed themselves, and the copper was rendered "red short." (Trans, Amer, Inst, Min. Engs.)
The common impurities found in commercial copper are-antimony, arsenic, bismuth, iron, lead, nickel, silver, sulphur, and tin. Antimony and sulphur reduce its malleability and tenacity. Arsenic in small proportion does not seem to have much effect, but when added to the extent of 1 in 10, it produces a white malleable alloy, much harder than copper, and not easily tarnished; this alloy is made by heating 5 parts copper shreds with 2 of white arsenic in alternate layers under a coating of sodium chloride in a covered earthenware crucible, and is used for dials and scale-rods. Bismuth and nickel decrease the toughness of copper; lead, even 1/10 per cent., destroys its good qualities; phosphorus (1/2 per cent.) hardens it, augments its tenacity, and tends to preserve it in sea-water; while a little tin increases its toughness. All impurities seriously impair the electrical conductivity of copper. According to some tables relating to pure copper wire for electrical purposes, issued by W. T. Glover & Co., of Manchester, pure copper weighs 555 lb. per cub. ft.; the resistance of 1 mil. foot at 60° F. (15 1/2° C.) is 10.32311 ohms; the resistance varies with the temperature at about 0.21 per cent. per 1° F., or 0.38 per 1° C.; a stranded conductor of a given length has a greater weight and a less resistance than an equal length of the same number of wires unstranded; No. 0000 BWG wire is 0454 in. diameter, 0.161883 sq. in. in area, weighs 0.623924 lb. per ft., measures 1.60276 ft. per lb., and has a resistance of 0.000050084 ohm per ft., or 19966.5 ft. per ohm, or 12457.5 lb. per ohm, or 0.000080272 ohm per lb.; while the corresponding figures for 30 BWG wire are 0.012 in. diameter, 0.000113097 sq. in. area, 0.0004359 lb. per ft., 2294.13 ft. per lb., 0.07168825 ohm resistance per ft., or 13.9493 ft. per ohm, or O.OO608041b. per ohm, or 164.462 ohms per lb.
Tubes are either rolled by machinery and the edges brazed together, or they are drawn in such a way as to be seamless. From § in. to 5 in. external diameter are the usual limits of size for brazed tubes, and beyond these sizes they are made by coppersmiths, and-not by tube-makers. Solid-drawn copper tubes are made up to 9 in. diameter; solid-drawn brass tubes are made of all sizes between 1/2 in. and 4 in. external diameter. The quality of brass tubes depends not only on the manufacture, but on the alloy of the brass. Tubes are usually made in lengths of 14 ft. to 16 ft., and are sold by lineal measure.
For bending copper tubes, the almost universal practice is to fill the tubes with lead or rosin, then bend them round a chuck or something of the same radius as that required for the bend. The lead or rosin may then be melted out. A machinist at Philadelphia, some years ago, devised an ingenious apparatus for this purpose, which, however, has not come into general use. It consists of a flexible mandrel of steel, made of wire of square cross-section, and with the coils lying in contact so as to form a close spiral. By inserting one of these of the right diameter into the. tube, it can be bent to any angle without showing the slightest symptom of wrinkling; when properly. bent, the mandrel can be readily withdrawn by simply taking hold of one end of it and drawing on it, giving it at the same time a slight twist to lessen its diameter. At the time this invention was first brought out it was said to answer its purpose very well.