GB/T 14635-2020Rare earth metals and their compounds - Determination of total rare earth content (English PDF)

2.2 Reagents and materials

2.2.1 Perchloric acid (rho=1.67g/mL).

2.2.2 Hydrogen peroxide (30%).

2.2.3 Hydrochloric acid (1+1).

2.2.4 Nitric acid (1+1).

2.2.5 Ammonia water (1+1).

2.2.6 Oxalic acid solution (50g/L).

2.2.8 Oxalic acid lotion (2g/L).

2.4 Specimen

2.4.1 The oxide layer on the surface shall be removed from the metal specimen and weigh immediately after sampling.

2.5 Analytical procedures

2.5.1 Testing materials Weigh the specimen (2.4) according to Table 4, accurate to 0.0001g.

2.5.2 The number of determinations Weigh two portions of testing materials for parallel determination, and take the average value.

3.3 Specimen

3.3.1 The surface oxide layer shall be removed from the metal specimen; and weigh immediately after sampling.

3.3.2 There are many types of rare earth compounds and their chemical properties are different. The basic state of the different compound specimen to determine the total rare earth content is difference. The basic state of measurement for each different compound is shown in Table

8.There are usually 3 ways.

3.4 Analysis procedures

3.4.1 Testing materials Take the specimen (3.3) according to Table 9, accurate to 0.0001g.

3.4.2 The number of determinations Weigh two specimens for parallel determination, and take the average value.

3.4.3 Determination

3.4.3.1 Dissolution of the testing materials 3.4.3.1.5 Dissolution of rare earth chloride. place the testing materials (3.4.1) in a 200mL beaker; add 20mL of water, 10mL of hydrochloric acid (3.2.5); cover with a watch glass; and take it off and cool to the room temperature after heating at low temperature to dissolve completely. Transfer the solution into a 200 mL volumetric flask; dilute to the mark with water, and mix well.

3.5 Calculation and expression of analysis results

3.5.1 Calculation and expression of the total rare earth content in rare earth metal testing materials

3.5.2 Calculation and expression of the total rare earth content in the rare earth compound testing materials The determination results of the total rare earth content in each rare earth compound are all the total rare earth content in the specimens with corresponding measurement basic state. The total rare earth content is calculated by the mass fraction w (REO) of rare earth oxide (REO), which is calculated as per Formula (5).

3.5.3 The calculation and expression of the total rare earth content in the mixed rare earth metal testing materials with heavy rare earth holmium, erbium, thulium, ytterbium and lutetium as the main body

3.5.4 The calculation and expression of the total rare earth content in the mixed rare earth compound testing materials with heavy rare earth holmium, erbium, thulium, ytterbium, and lutetium as the main body

3.6 Precision

3.6.1 Repeatability For the measured values of two independent test results obtained under repeatability conditions, within the average range given below, the absolute difference between the two test results does not exceed the repeatability limit (r);

3.6.2 Tolerance The difference between the analysis results among laboratories shall be no greater than the tolerance listed in Table 11.