Oxide of chromium and chrome iron ore have been proposed as refractory crucible materials.
The handle D, acting through the gear wheels E, F, G and H, turns the cogwheel K, which moves the curved rack of the cradle and tips the crucible M.
Second, their heat is applied far more economically, directly to the metal itself, whereas in the crucible process the heat is applied most wastefully to the outside of the non-conducting walls of a closed crucible within which the charge to be heated lies.
The crucible and the channel form the two limbs of an inverted siphon.
The examination of small test-pieces of the glass withdrawn from the crucible by means of an iron rod having shown that the molten mass is free from bubbles, the stirring process may be begun, the object of this manipulation being to render the glass as homogeneous as possible and to secure the absence of veins or striae in the product.
High, and heated either in a muffle or in a crucible furnace at a gradually increasing heat for forty or fifty minutes.
A precipitate of ruthenium oxide gradually separates; this is collected and ignited in a graphite crucible and finally fused in the oxyhydrogen furnace (H.
This uranate when ignited in a platinum crucible leaves a green oxide of the composition U308, i.e.
The crucible is of metal and considerably larger than the ingot, the latter being surrounded by a mass of unreduced material which protects the crucible from the intense heat.
The fusion process is preferably carried out in crucible furnaces; shaft furnaces are unsatisfactory on account of the disintegrating action of the molten bismuth on the furnace linings.