Color Reactions with the Fluxes

Some elements, when dissolved I n certain fluxes, give a characteristic color to the fused mass the fluxes that are most commonly used are borax, Na₂B₄O₇.10H₂O, sodium carbonate, Na₂CO₃, and salt o phosphorus, HNaNH₄PO₄.4H₂O. The operation is best performed by firs fusing the flux on a small loop of platinum wire into the from of a less-shaped bead.  The loop on the dire should best have the shape and size shown in Fig. 205 . After the flux has been fused into a bead o n the wire, a small amount of the powdered mineral is introduced into it and is dissolver by further heating. The color of the resulting bead may depend upon whether it was heated in the oxidizing or reducing flame and whether the bead is hot or cold. The following tale gives a list of the important bead tests:

Table of Color Reactions With the Fluxes

Oxides of		Borax Bead		Phosphorus Salt Bead
		Oxiding flame	Reducing flame	Oxiding flame	Reducing flame
Chromium	Hot.	Yellow	Green	Dirty green	Dirty green
	Cold.	Yellowish green.	Green	Fine green	Fine green
Vanadium	Hot.	Yellow.	Dirty green	Yellow.	Dirty green.
	Cold.	Yellowish green almost colorless	Fine green	Yellow.	Dirty green
Uranium	Hot.	Deep yellow to orange-red.	Pale green.	Yellow.	Pale dirty green
	Cold.	Yellow.	Pale green to nearly colorless.	Pale greenish yellow.	Fine green.
Iron	Hot.	Deep yellow to orange – red	Bottle-green	Deep yellow to almost colorless.	Red-yellow to yellow-green.
	Cold.	Yellow.	Pale bottle-green	Yellow to almost colorless.	Almost colorless
Copper	Hot.	Green.	Colorless to green.	Green.	Brownish green.
	Cold.	Blue.	Opaque red with much oxide.	Blue.	Opaque red.
Cobalt	Hot.	Blue.	Blue.	Blue.	Blue.
	Cold.	Blue.	Blue.	Blue.	Blue.
Nickel	Hot.	Violet.	Opaque gray.	Reddish to brownish red.	Reddish to brownish red
	Cold.	Reddish brown.	Opaque gray.	Yellow to red-dish yellow.	Yellow to red-dish yellow.
Manganese	Hot.	Violet.	Colorless.	Greyish violet.	Colorless.
	Cold.	Reddish violet.	Colorless.	Violet.	Colorless.

Sodium carbonate with oxide of manganese gives when heated in the oxidizing flame an opaque bead, free when hot, bluish green when cold. When heated in the reducing flame the bead is colorless.