GB/T 20975.1-2018Methods for chemical analysis of aluminium and aluminium alloys—Part 1: Determination of mercury content (English PDF)

2.1 Method principle

The test portion is dissolved with hydrochloric acid-nitric acid mixed acid; the divalent mercury in the solution is reduced to mercury with stannous chloride; and on a cold atomic absorption mercury analyzer, at a wavelength of 253.7 nm, the absorbance of mercury vapor is measured, to calculate the mass fraction of mercury.

2.2 Reagents and materials

Unless otherwise stated, in the analysis, only identified guaranteed reagents and Grade 1 water are used.

2.2.1 Nitric acid (rho=1.42 g/mL).

2.2.2 Hydrochloric acid (rho=1.19 g/mL).

2.2.3 Mixed acid. Nitric acid (2.2.1), hydrochloric acid (2.2.2), and water are mixed in a volume ratio of (1+3+4).

2.2.4 Potassium dichromate solution (25 g/L). WEIGH 25 g of potassium dichromate, DISSOLVE in water; TRANSFER to a 1000 mL volumetric flask; USE water to dilute to volume, and MIX well.

2.2.5 Nitric acid-potassium dichromate solution. WEIGH 0.5 g of potassium dichromate and DISSOLVE in water; ADD 50 mL of nitric acid (2.2.1); TRANSFER to a 1000 mL volumetric flask; USE water to dilute to volume, and MIX well.

2.2.6 Stannous chloride solution (200 g/L). WEIGH 20 g of stannous chloride (SnCl2 · H2O); DISSOLVE it in 20 mL of hydrochloric acid (2.2.2); TRANSFER to a 100 mL volumetric flask; USE water to dilute to volume, and MIX well.

2.2.7 Standard stock solution of mercury (100 µg/mL). WEIGH 0.1354 g of mercury bichloride [w(HgCl2) >=99.95%] which has been thoroughly dried in a silica gel drier; and ADD 5 mL of nitric acid (2.2.1) and a small amount of water. After micro-heat dissolution, TRANSFER to a 1000 mL volumetric flask; USE nitric acid-potassium dichromate solution (2.2.5) to dilute to volume, and MIX well. 1 mL of this solution contains 100 µg of mercury.

2.2.8 Mercury standard solution (10 µg/mL). PIPETTE 10.00 mL of standard stock solution of mercury (2.2.7) in a 100 mL volumetric flask; USE nitric acid-potassium dichromate solution (2.2.5) to dilute to volume, and MIX well. 1 mL of this solution contains 10 µg of mercury. Prepared when used.

2.2.9 Mercury standard solution (0.1 µg/mL). PIPETTE 2.00 mL of mercury standard solution (2.2.8) in a 200 mL volumetric flask; USE nitric acid-potassium dichromate solution (2.2.5) to dilute to volume, and MIX well. 1 mL of this solution contains 0.1 µg of mercury. Prepared when used.

2.3 Instrument

Cold atomic absorption mercury analyzer.

2.4 Sample

The sample is processed into chips having a thickness of no more than 1 mm.

2.5 Analytical procedures

2.5.1 Test portion

Sample (2.4) is weighed according to Table 1, accurate to 0.0001 g. […]

3.3 Instrument

Atomic fluorescence spectrometer, with mercury hollow cathode lamp.

3.4 Sample

The sample is processed into chips having a thickness of no more than 1 mm.

3.5 Analytical procedures

3.5.1 Test portion

WEIGH 1.00 g of sample (3.4), accurate to 0.0001 g.

3.5.2 Number of determinations

The determination is performed twice independently, and the average is taken.

3.5.3 Blank test

A blank test is carried out along with the test portion (3.5.1).

3.5.4 Determination

3.5.4.1 PLACE the test portion (3.5.1) in a 400 mL beaker; ADD 30 mL of mixed […]