Solder tube
A soldering tube is an angled, approx. 5 mm wide metal tube with a mouthpiece on the longer leg and a nozzle on the shorter leg. It is used to examine minerals - especially metals - and in inorganic qualitative analysis as a preliminary sample. Air is blown through the nozzle into a flame, creating a sharp jet flame with which the sample material can be heated to a very high temperature. The sample material undergoes chemical reactions, melts or evaporates. In addition, electrons are thermally excited in the steam, resulting in a typical flame color . The color of the flame, the oxide deposits and the type of melt products provide initial information about the composition of the sample. In the simplest case, a candle or an oil lamp (for example with turpentine oil , rapeseed oil ) served as the flame source . Better results can be achieved with a laboratory spirit burner or luminous gas in a Bunsen burner . The most meaningful results are obtained with an almost colorless propane gas flame .
method
In order to create a steady, uninterrupted flow of air, the mouth is filled with air and the mouthpiece of the soldering tube is placed on the mouth. You blow air into the tube with your cheeks, adding to the air supply in your mouth by exhaling. If you place the soldering tube in the central, glowing flame and blow vigorously but evenly through the mouthpiece, you get an oxygen-rich, so-called oxidation flame . If the soldering tube is placed on the edge of the flame and only blown with a moderate flow of air so that no brightly shining flame is created, a reduction flame is generated .
In a recess in a piece of charcoal (ideally linden charcoal), a mixture of soda and powdered test substance is stirred. The mixture is usually first melted in an oxidizing manner and then reduced. Depending on the composition of the sample, small melt globules, metallic flakes or, under oxidizing conditions, oxide deposits on the colder areas of the charcoal are obtained. The color of the oxide deposits and the properties of the melt products ( ferromagnetism , ductility or brittleness ) allow initial conclusions to be drawn about the composition of the sample. If necessary, the procedure is repeated several times, e.g. B. repeated with the addition of cobalt nitrate solution and the color and properties of the melt products are assessed.
The “pearl sample ” offers a more precise determination: after the addition of borax or phosphates , the sample substance melts, some metals give the borax or phosphorus salt pearls a characteristic color. Another possibility for the preliminary test is to evaluate the flame color of the sample in a platinum loop , ideally with a hand spectroscope.
history
The examination with the soldering tube is called soldering tube trial art and is a method of the general trial art . According to the records of Jöns Jakob Berzelius, the soldering tube was first used in 1738 by the Swedish miner Anton von Swab to use the additional "blown air" to deflect a hot jet from a flame and thus examine minerals. Another pioneer of the method in Sweden was Sven Rinman (from 1746).
In the 19th century, the Freiberg Mining Academy was a stronghold of the art of soldering tubing and mineral analysis . Karl Friedrich Plattner (1800–1858) was particularly active here. He wrote the book with the title Probirkunst mit dem Löthrohre, ... (1835). It has been published and reworked several times. From 1842 to 1856 he was a professor of metallurgy and soldering tube experimentation.
However, the first publication on the soldering tube trial is from Gustav von Engeström ( An essay towards a system of mineralogy ) in English from 1770, in which he described the use of the blowpipe based on the experience of the Swedish miner Axel Frederic Cronstedt . A German translation ( Mr. Gustav von Engestrom's description of a mineralogical pocket laboratory and in particular the use of the blowpipe in mineralogy ) was published by AF Rose in Greifswald in 1782.
Justus von Liebig developed the solder tube sample as a preliminary sample for the qualitative analysis. This way of working was very common among chemists in the 19th century. For example, Liebig mentions the “peaking of the lips when kissing” as the effect of working with the soldering tube among the three characteristics by which one recognizes the chemist.
Web links
- Theodor Richter : Carl Friedrich Plattner's trial art with the soldering pipe . 4th edition. Verlag von Johann Ambrosius Barth, Leipzig 1865 ( digitized edition in the Google book search).
- Jöns Jakob Berzelius : Textbook of Chemistry, Tenth Volume: Chemical operations and devices, along with an explanation of artificial chemical terms . 3. Edition. Arnoldische Buchhandlung, Dresden and Leipzig 1841, keyword “Lötrohr”, pp. 337–414 ( digitized edition on Archive.org).
Individual evidence
- ↑ Gerhard Jander, Ewald Blasius: Textbook of analytical and preparative inorganic chemistry . Leipzig 1985, pp. 128, 369
- ↑ Hans Jürgen Rösler: Textbook of Mineralogy . Deutscher Verlag für Grundstofftindustrie, Leipzig 1981, pp. 176–177
- ^ Theodor Richter: Carl Friedrich Plattner's trial art with the soldering tube. Leipzig 1865, p. 3
- ^ Theodor Richter: Carl Friedrich Plattner's trial art with the soldering tube. Leipzig 1865, pp. 3-4
- ^ Catalog of the National Library of Australia, entry: Engestrom, Gustav von