Paragraph 4 REAGENTS
Glacial acetic acid.
Ammonia solution: dilute one volume of ammonia (ρ = 0.88 g/ml) with 3 volumes of water.
Ammoniacal silver solution, according to Tollens, freshly prepared: mix 500 ml silver nitrate solution (10 g per 100 ml) with 500 ml ammonia solution (4.2).
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Do not expose unnecessarily to light, heat or air.
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Safety precaution: when handling ammoniacal silver nitrate solution, safety goggles must be worn.
Concentrated sulfuric acid (ρ = 1.84 g/ml).
Potassium sulfate.
Copper oxide (CuO), 0.3-0.4 g for each determination or an equivalent quantity of copper sulfate pentahydrate (0.95-1.25 g) for each determination.
Sodium hydroxide solution, 30 g per 100 ml, ammonia free.
Sulfuric acid, 0.05 M solution.
Sodium or potassium hydroxide, 0.1 M solution.
Indicator solutions:
Mixed indicator:
Solution A: dissolve 1 g methyl red in 37 ml 0.1 M sodium hydroxide solution and make up to 1 litre with water.
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Solution B: dissolve 1 g methylene blue in water and make up to 1 litre. Mix 1 volume of A with 2 volumes of solution B.
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This indicator is violet in acid solution, grey in neutral solution and green in alkaline solution. Use 0.5 ml (10 drops).
Methyl red indicator:
Dissolve 0.1 g methyl red in 50 ml 95% ethanol, make up to 100 ml with water. Filter if necessary. This indicator (4 to 5 drops) may be used instead of the preceding one.
Anti-bump granules of pumice stone, washed in hydrochloric acid and ignited.
Potassium thiocyanate.