Sodium carbonate bead test

Sodium carbonate bead tests The sodium carbonate bead is prepared by fusing a small quantity of sodium carbonate on a platinum wire loop in the Bunsen flame a white, opaque head is produced. If this is moistened, dipped into a little potassium nitrate and then into a small quantity of a manganese compound, and the whole heated in the oxidizing flame, a green bead of sodium manganate is formed ... 

Dry test (blowpipe test). When a bismuth compound is heated on charcoal with sodium carbonate in the blowpipe flame, a brittle bead of metal, surrounded by a yellow incrustation of the oxide, is obtained. 

Dry tests a. Blowpipe test All cobalt compounds when ignited with sodium carbonate on charcoal give grey, slightly metallic beads of cobalt. If these are removed, placed upon filter paper, and dissolved by the addition of a few drops of dilute nitric acid, a few drops of concentrated hydrochloric acid added and the filter paper dried, the latter is coloured blue by the cobalt chloride produced. 

Dry test (blowpipe test) when antimony compounds are heated with sodium carbonate upon charcoal, a brittle metallic bead, surrounded by a white incrustation, is obtained. 

If the fluorine is combined with silica, the sample must first be fused with sodium carbonate and the cold melt tested. The fusion is best carried out in a bead on platinum wire. Carbonate and sulfide rocks should be ignited beforehand. Mineral waters are tested by evaporating 5 ml samples to dryness. 

Procedure. A drop of the test solution is taken up in a platinum loop and carefully evaporated to dryness over a very small flame. The loop is then heated to redness and dipped in a mixture of equal parts of sodium potassium carbonate and sodium peroxide, and a bead is made by inserting the loop repeatedly in the flame. The chromium is completely oxidized to chromate. The cold bead is dissolved in 1 or 2 drops of 1 1 sulfuric acid on a spot plate, and 1 or 2 drops of a 1 % alcoholic diphenylcarbazide solution added. A violet color indicates chromium. 

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