A preliminary test in qualitative inorganic analysis that can be a guide to the presence of certain metals. A small loop is made in the end of a platinum or Nichrome wire and heated in a Bunsen flame until red hot. It is then dipped into powdered borax, and the adhering solid is held in the hottest part of the flame where it swells up as it loses its water of crystallization and then shrinks, forming a colorless, transparent glass-like bead .
A minute sample to be tested is introduced into the bead and the color observed in in the lower, reducing, part of the flame, allowed to cool, and the color observed. It is then heated in the upper, oxidizing, part of the flame, allowed to cool, and the color observed again. The color is also noted when the bead is cold.
Characteristic colored beads are produced with salts of copper, iron, chromium, manganese, cobalt and nickel. After the test, the bead is removed by heating it to fusion point, and plunging it into a vessel of water.
Metal Oxidizing flame Reducing flame
Aluminum colorless (hot and cold), opaque colorless, opaque
Antimony colorless, yellow or brown (hot) gray and opaque
Barium colorless
Bismuth colorless, yellow or brownish (hot) gray and opaque
Cadmium colorless gray and opaque
Calcium colorless
Cerium red (hot) colorless (hot and cold)
Copper sky blue (hot and cold), opaque red, opaque
Iron yellow (hot and cold), opaque bottle-green, opaque
Manganese pink (hot and cold), opaque colorless, opaque
Cobalt deep blue (hot and cold), opaque deep blue, opaque
Nickel yellow-brown (hot and cold), opaque grey, opaque
Silver colourless (hot and cold), opaque grey, opaque
Vanadium colourless(hot and cold), opaque green, opaque
Uranium yellow-brown (hot and cold), opaqu green, opaque
Chromium green (hot and cold), opaque green, opaque
Platinum colourless(hot and cold), opaque grey, opaque
Gold yellow-brown (hot and cold), opaque grey, opaque
Tin colourless(hot and cold), opaque colourless, opaque
Titanium colourless (hot and cold), opaque yellow, opaque (hot) violet (cold)
Tungsten colourless(hot and cold), opaque brown, opaque
Magnesium colourless(hot and cold), opaque colourless, opaque
Molybdenum colourless(hot and cold), opaque yellow or brown, opaque
Strontium colourless(hot and cold), opaque colourless, opaque
Thorium colourless(hot and cold), opaque colourless, opaque
Yttrium colourless(hot and cold), opaque colourless, opaque
Neodymium colourless(hot and cold), opaque colourless, opaque
Praseodymium colourless(hot and cold), opaque colourless, opaque
Silicon colourless(hot and cold), opaque colourless, opaque
Germanium colourless(hot and cold), opaque colourless, opaque