Heat the substance on a piece of charcoal in the reducing flame of the blowpipe.
When mixed with sodium carbonate and heated on charcoal in the reducing flame lead salts yield malleable globules of metal and a yellow oxide-ring.
Analysis.-A borax bead dissolves uranium oxides in the reducing flame with a green, in the oxidizing flame with a yellow, colour.
In the reducing flame the bead becomes violet, more readily on the addition of tin; in the presence of iron it becomes blood-red.
To obtain a good reducing flame (in which the combustible matter, very hot, but not yet burned, is disposed to take oxygen from any compound containing it), the nozzle, with smaller orifice, should just touch the flame at a point higher above the wick, and a somewhat weaker current of air should be blown.
