طرز شناسایی برخی ترکیبات معدنی:
Aluminum
Solutions of aluminum salts yield with ammonia TS a white, gelatinous precipitate which is insoluble in an excess of ammonia TS. A similar precipitate is produced by sodium hydroxide TS or sodium sulfide TS, but it dissolves in an excess of either reagent.
Benzoate
Neutral solutions of benzoates yield a salmon-coloured precipitate with ferric chloride TS. From moderately concentrated solutions of benzoate, dilute sulfuric acid TS precipitates free benzoic acid, which is readily soluble in ether.
Carbonate
Carbonates and bicarbonates effervesce with acids, yielding a colourless gas which produces a white precipitate immediately when passed into calcium hydroxide TS. Cold solutions of soluble carbonates are coloured red by phenolphthalein TS, whereas solutions of bicarbonates remain unchanged or are slightly changed.
Ferrocyanide
To 10 ml of a 1% solution of the sample add 1 ml of ferric chloride TS. A dark blue precipitate is formed.
Nitrate
When a solution of a nitrate is mixed with an equal volume of sulfuric acid, the mixture cooled, and a solution of ferrous sulfate superimposed, a brown colour is produced at the junction of the two liquids. Brownish red fumes are evolved when a nitrate is heated with sulfuric acid and metallic copper. Nitrates do not decolourize acidified potassium permanganate TS (distinction from nitrites).
Nitrite
Nitrites yield brownish red fumes when treated with dilute mineral acids or acetic acid. A few drops of potassium iodide TS and a few drops of dilute sulfuric acid TS added to a solution of a nitrite liberate iodine which colours starch TS blue.
Peroxide
Solutions of peroxides slightly acidified with sulfuric acid yield a deep blue colour upon the addition of potassium dichromate TS. On shaking the mixture with an equal volume of ether and allowing the liquids to separate, the blue colour is transferred to the ether layer.
Phosphate
Neutral solutions of orthophosphates yield with silver nitrate TS a yellow precipitate, which is soluble in dilute nitric acid TS or in ammonia TS. With ammonium molybdate TS, a yellow precipitate, which is soluble in ammonia TS, is formed.