Aphlogistic lamp
The aphlogistic lamp is a safety lamp for miners developed by Humphry Davy in 1816 . This lamp also shines without an open flame, i.e. aphlogistic, and thus has a decisive advantage over other common miner's lamps at that time.
history
At the beginning of the 19th century , due to the start of industrialization, more and more hard coal was required as an energy source. This made it necessary to mine the coal from ever deeper seams in order to extract the necessary quantities of coal. While the mine gas (mostly methane ) could still escape from pits with little depth without any problems, the mine gas could not escape safely from greater depths at the time because of the poor ventilation . This often explosive mixtures formed in the deeper levels from mine gas and air that firedamp was called. However, since good lighting is essential underground, this posed major problems for the miners, as initially only pit lights with open flames were available. The open flames often led to firedamp explosions in the pits, and lighting options were sought that would not cause explosions. In 1815, the English chemist Humphry Davy was asked to develop a safe miner's lamp. First, a steel wheel was used, which dragged past a flint, throwing sparks in order to illuminate the pits. This could not completely prevent the explosions and had a relatively low luminosity. At the beginning experiments were also carried out with luminous phosphor , luminous stones and even with electric light. Davy had already observed in 1801 that a platinum wire glows and emits light when it is strongly heated by a current. However, none of these methods brought the desired success and Davy first turned to researching the properties of mine gas. When he used various heat sources for the investigation, he found that the gas-air mixture without an open flame has a relatively high ignition temperature of 595 ° C. In order to make the common miner's lamps safe, the open flame was now surrounded with a metal wire mesh, whereby the heat of the flame was dissipated very quickly, whereby the temperature of the lamp is pushed below the explosion limit of the firedamp. This technology was explosion-proof even when the wire mesh was heated to red hot.
A remaining disadvantage was that in the event of a mine explosion or lack of oxygen, the flame in the lamp would go out and the miner would find it difficult to get to safety without light. Many miners died at that time, even if they were spared the actual explosion. To solve this problem, Davy used a discovery he had made as early as 1816. He had observed a mixture of air and methane reacting on a preheated platinum wire without a flame. So much heat is released that the platinum wire starts to glow. The glow continued even if the miner's lamp went out due to a lack of oxygen or the pressure wave of the explosion. With this experience he improved the existing technology of the miner's lamps.
technology
Davy used the existing safety pit lamps and improved them by attaching a spiral-shaped platinum wire to the wick of a spirit lamp in such a way that the coils protruded beyond the wick and into the flame. These coils were heated by the flame and, even after the flame was extinguished, remained glowing until all the gas was used up. This lamp was then brought onto the market in various forms and was widely used because it was easy to manufacture.
Disadvantages of this lamp were the still relatively low luminosity and the unpleasant odor that it gave off after the harmful ethanal . In addition, the high price of platinum as a raw material was a disadvantage. However, this was offset by the advantages mentioned. In addition, a new fire could be kindled at any time on the glowing wire.
reaction
In the main reaction, alcohol is reacted with oxygen.
The most important side reaction is the conversion of ethanol into ethanal in the absence of oxygen .
The reaction takes place catalytically , with the metal wire as a catalyst .
variants
Alternatives to platinum are the following materials in decreasing effectiveness: platinum> copper > copper ( silver-plated )> constantan > nickel . Other wires have shown themselves to be not reactive enough or - such as silver - do not withstand the heat.
Methanol , petroleum ether , acetone , ether and other fuels were also used as alternative fuels . However, when the toxic methanol was converted, formaldehyde was produced , which is why this turned out to be unsuitable. In contrast, alcohol was considered beneficial. Only with petroleum ether did the strong odor of the unhealthy ethanol fail to appear.
Individual evidence
- ↑ www.duden.de accessed on January 17, 2019.
- ↑ a b c I. L. Comstock: Comstock: About the aphlogistic lamp, or the lamp without a flame . In: Johann Gottfried Dingler (Ed.): Polytechnisches Journal . tape 9 . JG Cotta, Stuttgart 1822, p. 178–183 ( hu-berlin.de - the term catalysis was first coined in 1835. Ignoring the different catalytic effects of different metal surfaces, the article emphasizes their different thermal conductivities.).
- ↑ a b c d e f g Dietrich Buttner: The aphlogistic lamp after Humphry Davy . In: Science in the classroom - chemistry . tape 4 , no. 18 , 1993, p. 43-46 .