Latest / History of the Universe Physics & Electricity Vol. 3 / 024 - Electricity - Chapter 6 - History of Electric Lighting Part 2

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024 - Electricity - Chapter 6 - History of Electric Lighting Part 2 · History of the Universe Physics & Electricity Vol. 3

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  Speaker 1: Section twenty four of the Science History of the Universe,
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  Speaker 1: Volume three. This is a LibriVox recording. All LibriVox recordings
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  Speaker 1: in the public domain. For more information or to volunteer,
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  Speaker 1: please visit LibriVox dot org. Recording by Marianne The Science
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  Speaker 1: History of the Universe, Volume three, edited by Francis rold Wheeler. Electricity,
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  Speaker 1: Chapter six, History of electric lighting, Part two. Edison's first
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  Speaker 1: filaments were made of carbonized thread or paper. It is
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  Speaker 1: obvious that such filaments could not be made with any
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  Speaker 1: great uniformity. A great many experiments were made and are
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  Speaker 1: still being made to determine the best method of making them.
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  Speaker 1: They are, all, however, made by what is called the
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  Speaker 1: squirting process, of which an outline follows. Pure cellulose, as
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  Speaker 1: cotton wool or blotting paper is dissolved in a concentrated
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  Speaker 1: solution of saint chloride until a jelly like mass is obtained.
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  Speaker 1: Great care is required to obtain pure materials, and the
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  Speaker 1: various processes must be closely watched. This mass is filtered
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  Speaker 1: by forcing it through a suitable filter such as glass, wool,
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  Speaker 1: fine wire, gauze, or flannel. It is then heated under
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  Speaker 1: a vacuum to free the viscous material from air carried
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  Speaker 1: into it by the cotton wool or cellulose. It is
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  Speaker 1: then squirted under fairly high pressure through a fine orifice
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  Speaker 1: which just dips below the surface of acidified alcohol contained
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  Speaker 1: in a tall glass jar. The alcohol hardens the cellulose,
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  Speaker 1: which forms a fine thread of a diameter depending on
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  Speaker 1: the size of the orifice. By revolving the jar, the
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  Speaker 1: thread is coiled in it. When hard, it is removed
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  Speaker 1: and washed and wound on drums to dry. When dry,
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  Speaker 1: it has the appearance of catgut. It is then given
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  Speaker 1: the desired shape by being wound on molds and baked.
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  Speaker 1: Bundles of filaments are then packed in carbon powder in
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  Speaker 1: plumbago crucible which are raised to as high a temperature
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  Speaker 1: as possible. The carbonized filaments are gaged for diameter and
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  Speaker 1: the legs cut to the required length, after which they
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  Speaker 1: are ready for mounting on the leading in wires. There
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  Speaker 1: are two methods for doing this. In one, the ends
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  Speaker 1: are laid against the leading in wires and a drop
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  Speaker 1: of paste composed of graphite mixed with a binding material
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  Speaker 1: is applied, the paste being afterwards dried in an oven.
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  Speaker 1: The other by heating the joint red hot in an
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  Speaker 1: atmosphere of benzene. The benzene having decomposed and carbon deposited,
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  Speaker 1: the filament is then flashed in order to make it
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  Speaker 1: more uniform and increase its life. Flashing is accomplished by
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  Speaker 1: placing the filament under a bell jar filled with hydrocarbon
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  Speaker 1: vapor and raising it to incandescence by the passage of
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  Speaker 1: a current, whereupon the vapor is decomposed and a firm,
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  Speaker 1: compact coating of carbon is deposited upon it. The greatest
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  Speaker 1: deposit takes place where the filament is thinnest, as the
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  Speaker 1: current causes it to heat most in that part. Flashing
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  Speaker 1: therefore smooths out the irregularities of the filament. The filaments
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  Speaker 1: are next sealed into bulbs and the bulb exhausted. In
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  Speaker 1: the early days, sprangled mercury pumps were used, but these
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  Speaker 1: were very slow, although very perfect nowadays. A little phosphorus
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  Speaker 1: dissolved in alcohol is introduced into the stem, which is
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  Speaker 1: then connected to a mechanical air pump. Having oil sealed
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  Speaker 1: valves and exhausted as far as possible, The stem is
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  Speaker 1: then sealed for a short distance below the bulb and
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  Speaker 1: the phosphorus vaporized by a little heat into the bulb,
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  Speaker 1: where it combines with the remaining oxygen and completes the exhaustion.
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  Speaker 1: The lamp is then properly sealed off. The first patents
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  Speaker 1: covering the principles of the Nernst lamp were taken out
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  Speaker 1: by Professor W. Nernst in eighteen ninety seven and eighteen
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  Speaker 1: ninety eight. In its first form, it was very crude,
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  Speaker 1: serving mainly to show the fact that the filaments could
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  Speaker 1: be produced and that their efficiency was about twice that
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  Speaker 1: of the ordinary carbon fil filament. This was the first
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  Speaker 1: incandescent lamp to threaten the life of the Edison carbon
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  Speaker 1: filament lamp. Much was promised for it at first, and
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  Speaker 1: its development was vigorously taken up in this country, England
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  Speaker 1: and Germany. Although the lamps are still manufactured, very fewer
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  Speaker 1: in use and it is probable that the manufacture of
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  Speaker 1: them will soon cease entirely. The recent introduction of the
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  Speaker 1: tungsten lamp has made its existence unnecessary, as it is
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  Speaker 1: suppressed by the tungsten lamp inefficiency life and first cost.
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  Speaker 1: It contains, however, a very interesting principle viz. The employment
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  Speaker 1: of an electrolic conductor as the incandescent body. The conductor,
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  Speaker 1: or glower as it is called, is practically non conducting
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  Speaker 1: at ordinary temperatures, and requires to be heated before it
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  Speaker 1: will allow the passage of current through it. This fact
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  Speaker 1: is probably the principal cause of its failure commercially, as
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  Speaker 1: the heating apparatus is quite complicated of uncertain life, and
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  Speaker 1: the time consumed in lighting sometimes half a minute, is
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  Speaker 1: in many cases objectionable. This is the only electric lamp
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  Speaker 1: that can be started with a match and blown out.
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  Speaker 1: The glower of the American form of Nernst lamp is
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  Speaker 1: said to consist of the oxides of several rare metals
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  Speaker 1: such as ytrium, utribium, thorium, et cetera, although the true
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  Speaker 1: composition is known only to a few. The glowers are
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  Speaker 1: in the form of a short, thick filament cemented to
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  Speaker 1: flexible platinum terminals by which it is suspended below and
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  Speaker 1: close to heating coils consisting of porcelain tubes in which
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  Speaker 1: are embedded resistance wires. These resistance coils are of course
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  Speaker 1: necessary to bring the glower up to the temperature at
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  Speaker 1: which it begins to conduct The heating resistance is connected
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  Speaker 1: in shunt with the glower, which has in its immediate
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  Speaker 1: circuit an electromagnetic switch for opening the heater circuit. When
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  Speaker 1: the glower becomes sufficiently heated to conduct the current in
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  Speaker 1: this portion of the circuit, operates the electromagnetic switch and
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  Speaker 1: automatically cuts out the heating coils as the glower conducts
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  Speaker 1: electrolytically rather than as a solid. Up to the present
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  Speaker 1: it has given a much shorter life when used on
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  Speaker 1: direct or low frequency alternating current circuits than with higher frequencies.
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  Speaker 1: Although up to the present time these lamps cannot be
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  Speaker 1: called a commercial success, recent developments and improvements in constructional
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  Speaker 1: details have made the efficiency of the lamp equal to
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  Speaker 1: that of tungsten. If a method of producing a lamp
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  Speaker 1: free from the complicating starting apparatus which now prevails is discovered,
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  Speaker 1: these lamps may be heard from again. These lamps have
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  Speaker 1: followed one another in such rapid session that some of them,
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  Speaker 1: although full of promise, have never been long in the
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  Speaker 1: commercial field, having been succeeded by others. Still better. Incandescent
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  Speaker 1: electric lamps with metallic filaments are older than carbon filament lamps,
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  Speaker 1: as long ago as eighteen forty, lamps were constructed with
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  Speaker 1: filaments of platinum, and for thirty years after that date,
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  Speaker 1: various attempts were made to construct a practical lamp using
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  Speaker 1: either platinum or iridium wires for the filaments, the only
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  Speaker 1: two metals at all suitable which were obtainable at the time.
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  Speaker 1: None of these attempts met with any commercial success, and
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  Speaker 1: the use of metals was finally abandoned in favor of
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  Speaker 1: carbon by the experimenters who developed the carbon filament lamp
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  Speaker 1: in eighteen seventy eight to eighteen eighty. The success attained
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  Speaker 1: with carbon caused all consideration of metallic filaments to be
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  Speaker 1: put on one side for nearly twenty years. The introduction
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  Speaker 1: of the Nernst lamp appears to have then stimulated research afresh,
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  Speaker 1: and many investigators turned their attention to the metals to
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  Speaker 1: find the field greatly widened by the chemical progress which
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  Speaker 1: had been made in the meantime. Instead of only two
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  Speaker 1: possible metals to work with, there were now numbers known
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  Speaker 1: with sufficiently high melting points to suggest great possibilities. After
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  Speaker 1: much painstaking effort and laborious work carried out by inventors
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  Speaker 1: who deserved the highest possible praise for both their ingenuity
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  Speaker 1: and their perseverance. Three commercial metallic filament lamps have been
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  Speaker 1: evolved which have entirely altered the outlook for the future
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  Speaker 1: of the electric lighting industry. It is possible, suggests Maurice
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  Speaker 1: Solomon in his Electric Lamps, that these may prove to
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  Speaker 1: be only the forerunners of further improvements. Rumors of fresh
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  Speaker 1: developments are of almost weekly occurrence, and it is difficult
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  Speaker 1: to say at the moment what is likely to be
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  Speaker 1: the course of events during the next few years. Up
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  Speaker 1: to the present, none of the rumored improvements have given
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  Speaker 1: any evidence of being advanced beyond the laboratory stage, and
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  Speaker 1: many do not appear even to have reached that stage,
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  Speaker 1: though some have been proved commercial, namely the osmium to
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  Speaker 1: tellum and tungsten Wolfram or Orsome lamps. The osmium lamp
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  Speaker 1: is the invention of doctor Auer van Velsbach, and the
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  Speaker 1: earliest patents relating to it were taken out in eighteen
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  Speaker 1: ninety eight. The earlier reports in reference to the osmium
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  Speaker 1: lamps appeared in the technical press in nineteen o one,
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  Speaker 1: but the lamp does not appear to have been manufactured
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  Speaker 1: commercially until nineteen o three, and it was not until
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  Speaker 1: nineteen o five that it was introduced into this country
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  Speaker 1: by the General Electric Company. The method of manufacture may
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  Speaker 1: be gleaned from the patents and from a paper read
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  Speaker 1: by doctor Fritz Blau before the electrotechhnecher Varine in nineteen
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  Speaker 1: o five. The process first tried was that a flashing
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  Speaker 1: platinum wire in an atmosphere of osmium textroxide, which is volatile.
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  Speaker 1: By subsequently in condensing the alloy in vacuo, the platinum
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  Speaker 1: can be evaporated off, but it was not found possible
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  Speaker 1: to produce sufficiently thin filaments in this way. Finally, the
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  Speaker 1: method adopted was that of pressing finely divided osmium mixed
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  Speaker 1: with an organic binding agent through small diamond or sapphire dyes.
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  Speaker 1: The thread thus formed is carbonized and the carbon is
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  Speaker 1: then driven off by encasing the filament in an atmosphere
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  Speaker 1: of steam and hydrogen. The filaments have to be raised
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  Speaker 1: to a very high temperature in order to center together
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  Speaker 1: the osmium particles into a practically homogyeneus filament. Cinering may
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  Speaker 1: be described as a sort of modified welding process. The
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  Speaker 1: metal does not fuse, but the particles, raised almost to
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  Speaker 1: their melting point, baked together and bind very firmly. As
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  Speaker 1: a matter of fact, exactly the same phenomenon occurs with
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  Speaker 1: carbon filaments, which after the first stages of baking, are
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  Speaker 1: highly porous, but become dense and homogeneous on further raising
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  Speaker 1: their temperature. The osmium filaments are mounted in bulbs in
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  Speaker 1: the same way as carbon filaments, the mount being made
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  Speaker 1: by fixing together by means of an arc at the
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  Speaker 1: end of the osmium filament and the leading in wire.
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  Speaker 1: The osmium lamp has been described on account of its
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  Speaker 1: interesting position as the first of the new metallic filament lamps.
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  Speaker 1: The lamp must be regarded at present as already obsolete,
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  Speaker 1: having given place to the tungsten lamp, the filament of
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  Speaker 1: which is similar in character to the osmium filament, but
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  Speaker 1: in many respects superior. The earliest patents in relation to
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  Speaker 1: the tantalin lamp were taken down by Messrs Seamen and
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  Speaker 1: Hulsk in nineteen o one. In nineteen o two, but
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  Speaker 1: the lamp was not introduced commercially until nineteen o five.
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  Speaker 1: During nineteen o six and nineteen o seven. The lamp
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  Speaker 1: has steadily grown in popularity and the number now in
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  Speaker 1: use is very large. The tantalum lamp can certainly claim
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  Speaker 1: to be the first metallic filament lamp which proved to
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  Speaker 1: the full its suitability by the development of its formidable rival,
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  Speaker 1: the tungsten lamp, and it will continue to be remembered
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  Speaker 1: as the first lamp to afford solid ground for the
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  Speaker 1: hope of a marked at vance in electric incandescent lighting.
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  Speaker 1: The filament of the tantalum lamp is made from pure
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  Speaker 1: drawn tantalum wire, and one of the chief difficulties in
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  Speaker 1: its manufacture is a preparation of the pure tantalum in
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  Speaker 1: a form suitable for drawing. Tantalum metal is obtained in
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  Speaker 1: a powdery form by reducing potassium tantalofluoride. The powder is
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  Speaker 1: then fused electrically in vaccio, the process serving not only
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  Speaker 1: to produce the metal in a coherent form, but also
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  Speaker 1: to drive off the occluded gases. The fuse ingot is
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  Speaker 1: drawn into wire. The precise method by which this is
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  Speaker 1: done not being published, but the process must be one
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  Speaker 1: of considerable difficulty in view of the extreme hardness of
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  Speaker 1: the metal, which is, however, ductile, and the tantalum wires
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  Speaker 1: are quite flexible. The metal oxidizes readily, and when heated,
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  Speaker 1: burns away completely to oxide. The filament must therefore be
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  Speaker 1: mounted in an exhausted bulb, and the difficulty of disposing
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  Speaker 1: of the necessary length in the bulb has been overcome
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  Speaker 1: in an ingenious manner, rendered possible by the flexibility of
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  Speaker 1: the wire, by winding it on a frame, as shown
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  Speaker 1: in Fig. Twenty nine. In this figure, for the sake
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  Speaker 1: of greater clearness, only the front half of the frame
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  Speaker 1: and filament is shown. This frame is mounted in a
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  Speaker 1: bulb in the usual manner. The other details of the
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  Speaker 1: lamp call for no special mention. Probably apart from the
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  Speaker 1: difficulty in making the original tantalum wire, the lamp is
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  Speaker 1: one of the easiest of the metallic filament lamps to manufacture,
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  Speaker 1: which leads to the hope that it may be greatly
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  Speaker 1: reduced in price when competition renders this necessary. The earliest
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  Speaker 1: patents relating to production of filaments of tungsten appear in
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  Speaker 1: nineteen o four. The most important of these are taken
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  Speaker 1: out by Just and Hannemann. Kutzel and Velsbach in nineteen
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  Speaker 1: o five and nineteen o six. Many other patentees covered
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  Speaker 1: processes for manufacturing these filaments, but it must be remembered
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  Speaker 1: that by this time the possibilities of the metallic filament
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  Speaker 1: lamp were becoming well recognized, and many who patented methods
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  Speaker 1: and processes probably did so only in the hope that
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  Speaker 1: their ideas might some day prove fruitful. The credit for
• 13:36
  Speaker 1: the development of a commercial lamp rests with the inventors
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  Speaker 1: already named, and lamps are now manufactured by all three
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  Speaker 1: of the processes which they devised. It is true early
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  Speaker 1: to say which of these is likely to survive. Possibly
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  Speaker 1: some modification combining the advantages of all will prove ultimately
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  Speaker 1: the most efficient and reliable manufacturing process. The tungsten lamp
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  Speaker 1: appears to have a brilliant future before it. While its
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  Speaker 1: present form lacks some of the advantages of the ten
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  Speaker 1: tallum lamp, the fact that the consumption of power per
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  Speaker 1: candle is only about half that with tentalum will cover
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  Speaker 1: a great many defects. Unless a new metal filament is
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  Speaker 1: brought forward with an efficiency markedly superior, it is difficult
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  Speaker 1: to see what competitor now in the field can stand
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  Speaker 1: long against the tungsten filament. The commercial development of the
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  Speaker 1: tungsten lamp has been conducted with marvelous rapidity everywhere they
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  Speaker 1: are rapidly displacing carbon filament lamps. Their frigility, however, restricts
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  Speaker 1: their use to places where they are not subjected to
• 14:35
  Speaker 1: mechanical vibration, although by ingenious methods of mounting this defect
• 14:39
  Speaker 1: is fast being overcome. The idea of producing light from
• 14:43
  Speaker 1: incandescent vapors has always been an attractive one. Theoretically, it
• 14:47
  Speaker 1: is possible to obtain a far more efficient light from
• 14:50
  Speaker 1: these vapors than from incandescent solids, because the emanations are
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  Speaker 1: more nearly of the same frequency than those from solids.
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  Speaker 1: Discharges in vacuum tubes have been tried for many years,
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  Speaker 1: and there was developed a form of tubes known as
• 15:05
  Speaker 1: Geisler tubes, in which the most beautiful effects were produced
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  Speaker 1: by discharges through rarefied gases, but their brightness was never
• 15:12
  Speaker 1: sufficient for practical lighting. About ten years ago, Peter Cooper Hewitt,
• 15:17
  Speaker 1: making use of the fact that a column of mercury
• 15:19
  Speaker 1: vapor is a good conductor, succeeded in constructing a mercury
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  Speaker 1: vapor lamp of great power and efficiency. The lamp consists
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  Speaker 1: of a long glass tube having two electrodes, the negative
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  Speaker 1: of which is mercury. The arc is formed between these
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  Speaker 1: electrodes and completely fills the tube. This is therefore a
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  Speaker 1: true arc lamp. The lamp must be burned in an
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  Speaker 1: inclined position, the mercury being in constant circulation. It is
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  Speaker 1: vaporized at the lower end, condensed at the upper and
• 15:47
  Speaker 1: runs back to the lower again. One feature, which for
• 15:51
  Speaker 1: general lighting is objectionable is the color distortion produced by
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  Speaker 1: this light. Since there are no red rays in it,
• 15:58
  Speaker 1: red bodies appear black, and all objects have a greenish
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  Speaker 1: blue appearance for purposes of photography, for drafting rooms, et cetera.
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  Speaker 1: It is, however, admirable, being rich in the upper rays
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  Speaker 1: of the spectrum. Following out the idea of producing light
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  Speaker 1: from discharges in a vacuum, MacFarlane Moore has succeeded in
• 16:16
  Speaker 1: producing a lamp which is extremely ingenious. The chief advantage
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  Speaker 1: claimed is the improved distribution of the light, the light
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  Speaker 1: being nowhere intense. The tubes may be made a hundred
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  Speaker 1: or two feet long and may be fitted to suit
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  Speaker 1: the shape of the room. The discharge is affected by
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  Speaker 1: means of a high voltage transformer. The tube gives off
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  Speaker 1: a pleasing light of a pink color. End of Chapter
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  Speaker 1: six