Cadmium salts can be recognized by the brown incrustation which is formed when they are heated on charcoal in the oxidizing flame of the blowpipe; and also by the yellow precipitate formed when sulphuretted hydrogen is passed though their acidified solutions.
The operation is repeated with the thread in the oxidizing flame.
The dressed ore is introduced through a "hopper" at the top, and exposed to a moderate oxidizing flame until a certain proportion of ore is oxidized, openings at the side enabling the workmen to stir up the ore so as to constantly renew the surface exposed to the air.
Analysis.-A borax bead dissolves uranium oxides in the reducing flame with a green, in the oxidizing flame with a yellow, colour.
Titanium oxide when fused with microcosmic salt in the oxidizing flame yields a bead which is yellowish in the heat but colourless after cooling.
