Crucible
A crucible is a fire-proof and chemically resistant vessel for heating materials or for the production of melts . It can e.g. B. made of ceramic ( fireclay , alumina , zirconium oxide and graphite ), glass or metal .
variants
In the laboratory , crucibles in a typical shape with a tapered bottom are used so that they can be heated in a flame in a clay triangle . Porcelain crucibles are usually only used once. In addition to porcelain, nickel , platinum and quartz glass are the most common materials for crucibles. Platinum crucibles can be used at very high temperatures without being attacked. With some other sample materials, however, there is a risk of cracking or chemical attack. Quartz glass crucibles are extremely resistant to temperature changes and can be quenched red-hot in cold water without suffering any damage. A lid is often used to prevent evaporation and to prevent the inside from cooling down.
A crucible shoe is a low-walled container made of porcelain in which the crucibles are placed. Crucible shoes prevent the furnaces from getting dirty if the crucible overflows or breaks.
A special case is the Rose crucible , which is used to heat solid substance samples in a gas stream. It is covered with a perforated lid, through the opening of which an angled porcelain tube is used to supply the gas in question.
In Saxon and Thuringian, crucible often means a frying pan . Conversely, pan refers to a large industrial crucible used in steel manufacture ( steel casting ladle ).
Labeling of porcelain crucibles
For permanent labeling of porcelain crucibles, the numbers are applied thinly to the bottom of the crucible using an aqueous solution of a cobalt salt (e.g. cobalt (II) nitrate ). Then these are dried and annealed, the lettering then remains permanently legible in black.
