Polytechnic Association of the American Institute. (Zinc)

Scientific American 8, 18.2.1860

[Reported expressly for the Scientific American.]

In our last issue, we published Professor C. Mason's interesting paper on the subject of "Zinc," read by him at the regular meeting of the above association, in their room in the Cooper Institute, this city, on the 26th ult.; but we were compelled to defer, until this number, the publishing of the subsequent and equally interesting

DISCUSSION.

Mr. Seely said: — "The mention of Paracelsus, by the president, reminds us of alchemy, of which Paracelsus was the great apostle; he made it his sole business to search for the philosopher's stone and the elixir vitæ; he is reputed to have discovered the latter and to have used it himself, and yet he died young. The ore of zinc called 'calamine' was very nearly what the the alchemists imagined to be the philosopher's stone; they melted copper with it, and, to their minds, the copper was transmuted into a metal nearer like gold. Had Paracelsus produced that species of brass we call 'oreide,' the people of his time would not have doubted that he had really found in calamine all that he sought, for the modern oreide satisfies their notions of gold. Brass, until 80 years ago, was made by the ancient process of melting (in a crucible) copper mixed with charcoal and an ore of zinc. At present, we first melt one of the metals, then add the other. If copper be melted first, zinc in lumps is put in, and held sander the surface; if zinc is melted first, copper is gradually added, finely granulated or in shavings or turnings. If you try to melt both at the same time, the zinc will volatilize, carrying away heat, and the copper will not melt till the zinc has nearly all escaped — it is like trying to melt ice and lead at the same time. The properties of brass are measured by else proportion of zinc and copper — the more zinc, the whiter, snore brittle and more fusible; the more copper, the darker, more malleable and heavier. Halfandhalf gives Prince's metal; zinc to copper as l to 2, or 2 to 3, gives common,yellow brass; a greater excess of copper gives pinchbeck. Brass is not so malleable and ductile as copper; and, in order to get very thin brass or fine wires, sheets or wire of copper are covered over by a skin of brass, and then hammered or drawn out. Copper is brassed by plating or by exposure to fumes of zinc. Metallic bronze powders are brass foil of a great excess of copper made fine by grinding; the various colors are produced by heat. Brass does not remain uniform in successive meltings; it loses its zinc; the smoke about brass foundries is the oxyd of zinc. A little lead in brass improves it for turning. Zinc is strongly affected by heat; a little above the boiling point of water it becomes quite malleable, and may be rolled extremely thin; about 600°, it is so brittle as to be easily pulverized; at 800°, it melts, and begins to evaporate; and at a higher heat it will boil. The useful ores of zinc are the oxyd, the carbonate, the sulphide and the silicate; and their values are in the order named. The first two require only heating with coal to reduce them i the sulphide must first be roasted to drive off sulphur and convert to oxyd; and the silicate requires that the silicic acid, silex and quartz be token away — a thing not very easy. Thus, it appears that the ores must first be converted to oxyd before any metal is reduced; and when the metal is reduced, the heat converts it into vapor. In short, zinc oxyd mixed with coal is put in a retort, and the zinc is distilled off."

Mr. Seely then illustrated, by drawing on the blackboard, the forms of retorts (gas retort shapes, tubular and crucible) used in Germany, France and England.

Professes Mason remarked that, in treating of the metals, very little had been said about extracting them. He added that the silicate of zinc was no more costly to extract than white carbonate. Specimens of vitrified substances for fancy iron work had been produced; but something substantial, beautiful and ornamental might yet be brought forth for coating the walls of houses, iron columns, girders, &c.

Mr. Stevens, upon request, illustrated by diagrams the American mode of collecting white oxyd of zinc, called the "bag process." It was manufactured at about two cents a pound.

Professor Mason alluded to the competition manifested in the French and American white oxyd of zinc. He added that, in the manufacture of white lead, Satan apparently had as much to do with it as the Maker, from the number of deaths which its poisonous qualities produced. Its manufacture formerly was exclusive; it was even now so adulterated that a dealer told him he could trust only one house for this as well as zinc-white. The zinc-white of France is twice as costly as our own, but it is far superior; and, in both cases, the supply can hardly keep pace with the demand.

Dr. Gould had noticed, in soldering silver, that it always left a rough, broken margin, owing, probably, to the fact that silver was alloyed with copper and a little zinc; that the zinc fused at 700° and copper at 1,900°, and thus the zinc volatized, causing the roughness; and he asked whether anything could be proposed to prevent it?

Dr. Stevens answered that zinc, with a certain part of alumina, formed the best solder, and the zinc would volatilize; but it required care to avoid submitting it to too great a heat, or carrrying it to too great a length of time. It is remedied somewhat by a species of flux — by balsam of copaiba, instead of borax or resin. He could not give the reason. He added that zinc and lead paints were generally adulterated as other articles in commerce. For instance, flour was adulterated with barites to make it weigh heavy; plaster-of-Paris, by the sulphate of lime. So with medicines and drinks; so, also with furs that are made in factories. Names are given to animals of which dictionaries are dumb. The fitch marten, the English bear, and (stranger still) the Siberian wolf are examples. In an ounce of cochineal, there are hardly 20 grains that are pure; could it be wondered at, then, that paints were adulterated?

Professor Mason said that at the last fair of the American Institute, a zinc water pipe was exhibited and recommended.

Mr. Garvey said the pipe was very superior in workmanship, and was the first specimen of solid zinc pipe; it was not crystalline, but malleable; attached to it was a bathing apparatus complete. He would seek for further information concerning it.

Professor Mason was informed that block tin was sometimes alloyed and adulterated with zinc; was it practicable? Professor Draper and himself, aware of this fact, had fitted-up these pipes to convey water from a spring to their houses. In a few weeks the water would not run; it was examined, and the water was found to ooze like perspiration through the whole lengths of the pipe in the ground. Perhaps it could be accounted for by the alloy of zinc in the block tin occasioning the porosity of the metal.

Mr. Howe believed that tin was a poor metal for water pipes.

Mr. Montgomery advocated the adoption of wooden pipes, on account of their cheapness, non-conducting quality, and the fact that they were not likely to be affected by congelation. New York had made a retrograde step when it abolished the log pipes of the old Manhattan Company.

Mr. Garvey had recently seen pipes coated on the inside with a mineral substance which rendered them impervious to water, and which had the same degree of expansion as the metal, and was not likely to peel off. In wooden pipes, the grain of wood is such that it splits, and the outer surface would rot from moisture; but it might be coated with silica.

Mr Montgomery referred to wooden pipes which, after being in use for GO years, were as good as new. Lead pipes should be abolished; the more pure the water, the more fatal the lead.

Mr. Howe suggested that J. F. Green, of this city, had a material for safely coating any kind of metallic pipe.

Professor Mason then suggested the question of the qualities of brass and its alloys. Professor Tillman said: — "In making brass, the reason of zinc and copper uniting is not altogether known; it might be owing to the atomic weight, thus: zinc being 32.00, copper 27.22. The great characteristic of zinc is its expansibility, and it dissolves more readily than any other metal."

Professor Hendricks remarked that mercury had a uniting tendency with tin, and that it alloyed very readily.

Dr. Stevens stated, by request, that the sulphate was the poisonous quality in zinc, and therefore its pernicious use in water pipes.

Professor Mason said: — "There is no objection to mixing brass with iron, because the former is specifically heavier than the latter.

Mr. Johnson said: — "Alloy brass with Franklinite, and it hardens it, and is malleable and ductile. In reference to solder, a dentist in this city uses a solder which presents a certain temperature and color, and to use properly it is melted quickly and leaves a smooth surface.

Mr. Seely: — "The equivalent of alloys in brass are about the same; upon the alloy depends the quality of the brass. Prince's metal has equal parts. The difference of temperature makes the alloys unite very readily. A good copper wire has been exhibited by putting it in the fumes of zinc. Copper sheet is brassed by a kind of cementing process, as in steel, or by putting it in an atmosphere of zinc vapor, and brassing the surface only."

Professor Hendricks said it was almost like the method employed in New England to make brass watchchains look like gold.

Professor Mason said that 60 of zinc and 40 of copper made good brass.

Dr. Tying said, in reference to water pipes, that glass pipes had been used very successfully and healthfully in several cities, and cost less in proportion than wood.

Mr. Montgomery had manufactured glass pipes, but preferred wood, whatever kind it might be.

Professor Mason attributed the death of thousands to paralysis, caused by the lead pipes. He had lost several personal friends, he believed, from this cause.

Mr. Seely asked for information about chrome zinc.

Professor Hendricks said that there was a supposition of chrome yellow, and a very fine color.

Mr. Garvey said that the metal in question had been used for imitating "intaglio." Yellow was obtained, also, from the vegetable kingdom.

Mr. Seely had heard nothing but praise of zinc-white; but painters said it did not spread easy or color well. An artist of Paris had put it on canvas, and after a few months it peeled off.

Mr. Howe had found zinc-yellow to be deficient to chromate of lead, but the first has improved of late. He regarded zinc-white as the most durable and useful of colors.

A painter testified that a coat of white lead gave a good appearance, but zinc-white went under the wood, and it required four coats to equal the appearance of two coats of white lead. The reason of its peeling-off was that the first coat was not dry before the second was put on. He had tried Belgium, Pennsylvania and Lehigh; but he preferred the last. He had known many workmen in white lead to have lost their hands and arms by paralysis.

Professoi Mason deferred reading the practical report on "Franklinite," and moved that the subject of "Lead" be taken up at the next meeting. This resolution was carried, and the association then adjourned.