Gas mantle

A mantle or gas asset (also called mantle ) is a dome - or pear-shaped fine-mesh structure of oxides, which in gas-powered lights ( gas lamps and those that Petroleum - see Petromax - or other liquid fuels evaporate ) the light source is formed by passing it through the flame is stimulated to emit light. He is prepared Woven fabrics of cotton, silk or rayon made ​​from a rare earth with special salts that burns by heating in a gas flame and the salts leaves as oxides in the form of a fine framework.

Description

According to Kirchhoff's law of radiation gas flames barely light up because they have an emissivity close to zero in the visible light. In order to use gas lamps for light purposes, they were therefore previously operated with smoky gases that produce a yellowish light like a candle by glowing carbon particles.

Whiter brighter light was obtained by heating certain temperature-and oxygen- resistant materials. Carl Auer von Welsbach soaked a knitted mesh made ​​of cotton with a solution of rare earth salts, carefully burned the cotton and residue obtained was a delicate self -supporting structure of the cotton bag with the corresponding oxides. The method he patented on 23 September 1885 in Germany under the name Auer mantle.

Production

Previously, there were prepared Mantles by soaking cloth with a solution of 99 percent, slightly radioactive thorium nitrate and 1 percent cerium nitrate and then lit. In the heat of the thorium nitrate was divided into thorium dioxide and nitrogen oxides. This remained a fragile structure, which gave a white light in the gas flame. This lights had nothing to do with the very weak radioactivity of thorium, but is a common incandescence by the heat of the gas flame.

First used Carl Auer von Welsbach, magnesium oxide, zirconia, then lanthanum, yttrium and praseodymium compounds. They all point to a moderate emissivity in the visible range and produce only a brown white glow. His breakthrough came with cerium (IV ) oxide, together with thorium dioxide to improve stability. The composition of 1 % CeO2 and 99 % ThO2 was only a few decades ago replaced by a mixture of yttria and ceria, to dispense with the slightly radioactive ThO2 can.

Various forms of incandescent mantle

Mantles are available in many designs, the best known are probably the pouch- shaped to tie at Petromax and similar high-powered lamps, which must itself Flame the user to take it into operation. Not so common are Mantles for hanging or standing gas light that are already factory burned down and soaked with a nitro finish, so they get a higher strength for transportation. This lacquer layer burns when you first start off very quickly. The hanging mantles are usually spherical or pear-shaped; Related mantles hose or beehive- shaped. For the suspension of tissue, and for mounting on the burner of the lamp often moldings are made ​​of sintered magnesia.

The thermal emission of Auer mantle (dotted line in the diagram ) is significantly lower than that of a black body radiator ( blue line). In return, the radiation focused on the short-wavelength range in the visible spectrum. This takes the mantle at a higher temperature than it did a continuous-wave material. The red component is reduced, the light appears white.

At the high compared to an open flame luminous efficiency of incandescent mantles, however, principally by the direct energy transfer from the partially high-energy chemical reactants of the flame on electron levels of the cerium -doped phosphor in the mantle; in the oven heated gas mantles do not light nearly as bright as in the flame.

Through its luminosity of the mantle to this day against the electric light is competitive when no current connection to the electricity grid is available. However, the effective efficiency of about 5 lm / W, is only half as large as that of a light bulb, or only about one tenth of a modern gas discharge lamp. For this reason, light stockings for street lighting have greatly diminished.

Since then, the municipal gas works were abolished in the 1970s and natural gas flowing through the gas lines, the number of gas lanterns fell sharply. Instead of switching to natural gas, is often replaced them with the maintenance poorer and more effective, electrically operated gas discharge lamps.

In 2004, the last remaining in Germany Glühstrumpfproduktion the Berlin firm MSA GmbH was sold to the Indian company, Indo, a daughter of the consortium Prabhat Udyog Limited and shifted production to India. Indo offers both radioactive and non-radioactive gas mantle.

Since the thorium nitrate still used in part is slightly radioactive, such gas mantles may be imported only with a special permit to Germany. This was for example in Berlin a supply problem that has since been resolved. By the will of the operating company (formerly City Licht GmbH - now Vattenfall ) and the Mitte District, which was responsible for the remaining 43 908 public gaslights in Berlin, they should be abolished in the next few years - even at 50 kg low-level radioactive waste and 43,000 tonnes of to avoid carbon dioxide, and 700,000 cubic meters of otherwise unused save gas escaping.

Be used except in gas mantles gas lanterns in camping lights that are powered like camping stove with gas from the cartridge or with gasoline. There was also operated with spirit lamps, whose luminosity could be regulated by the height of the vertically sliding Brenntofftanks.