Paragraph 3 REAGENTS

3.1

Sodium hydroxide solution: 40 g per 100 ml, ammonia free.

3.2

Sulfuric acid, 0.05 M solution.

3.3

Sulfuric acid, 0.1 M solution.

3.4

Sulfuric acid, 0.25 M solution.

3.5

Sodium hydroxide, 0.2 M solution, carbonate free.

3.6

Chromium metal powder, 100 mesh, low nitrogen content.

3.7

Anti-bump granules of pumice stone, washed in hydrochloric acid and ignited.

3.8

Anti-foaming agent, paraffin wax.

3.9

sulfuric acid (ρ = 1.84 g/ml).

3.10

Hydrochloric acid (ρ = 1.18 g/ml).

3.11

Catalyst mixture: 1000 g potassium sulfate and 50 g copper sulfate pentahydrate. The ingredients must be ground and thoroughly mixed.

Indicator solutions

3.12

Mixed indicator:

3.12.1

Mix 50 ml of 2 g/litre ethanolic solution of methyl red with 50 ml of 1 g/litre ethanolic solution of methylene blue.

Methyl red indicator:

3.12.2

Dissolve 0.1 g methyl red in 50 ml ethanol. This indicator may be used instead of the preceding one.

3.13

pH indicator paper, wide range.