GB/T 4702.4-2008Chromium metal - Determination of iron content - EDTA titrimetric method and flame atomic absorption spectrometric method (English PDF)

3.1 Principle

Sample was dissolved with hydrochloric acid, perchloric acid smoke, made basic with ammonia to separate most of the chromium. Was dissolved in nitric hydroxide precipitate, add

The smoke perchlorate, chromium acid to produce a chlorinated volatile chromium residue was treated with hydrochloric acid, water and dissolved salts, the pH is adjusted to sulfosalicylic acid as indicator.

With disodium edetate titrate, according to the consumption of standard solution, the iron content calculated.

3.2 Reagents and materials

Unless otherwise indicated in the analysis using only recognized as analytical grade reagents and distilled water or its equivalent purity water.

3.2.1

ammonium chloride as a solid.

3.2.2

ammonia, rho0.90g/mL.

3.2.3

perchloric acid, rho1.67g/mL.

3.2.4

nitrate, rho1.42g/mL.

3.2.5

hydrochloric acid, rho1.19g/mL.

3.2.6

hydrochloric acid, 1 + 1.

3.2.7

hydrochloric acid, 1 + 2.

3.2.8

hexamethylenetetramine solution, 250g/L.

3.2.9

hexamethylenetetramine solution, 5g/L.

3.2.10

sulfosalicylic acid solution, 50g/L.

3.2.11 ammonia buffer solution, pH10

Weigh 67.5g of ammonium chloride (3.2.1) dissolved in water, aqueous ammonia was added 570mL (3.2.2), washed with water

Diluted to 1000mL, and mix.

3.2.12

iron standard solution, 0.1000mg/mL.

3.2.12.1

weighed 1.000g iron (more than 99.90%) were placed in 300mL beaker, add 30mL hydrochloric acid (3.2.7), thermal decomposition, […]