GB/T 14635-2020: Rare Earth Metals and Their Compounds - Determination of Total Rare Earth Content

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Scope

This Standard specifies the determination method of total rare earth content in the rare
earth metals and their compounds.
This Standard is applicable to the determination of the total rare earth content in rare
earth metals and their compounds. This Standard contains two methods. Method-1 is
oxalate gravimetric method, and Method-2 is EDTA titration method. Method-1 is
applicable to the determination of the total rare earth content in single and mixed rare
earth metals and their compounds; the determination range is shown in Table 1; it is
not applicable to the determination of the total rare earth content in single and mixed
rare earth metals and their compounds mainly based on erbium, thulium, ytterbium,
and lutetium or the individual content of thorium and lead is greater than 0.1%. Method-
2 is applicable to the determination of the total rare earth content in the single rare
earth metals and mixed rare earth metals and their compounds mainly based on heavy
rare earth holmium, erbium, thulium, ytterbium, and lutetium; the determination range
is shown in Table 2; it is not applicable to the determination of the total rare earth
content in the single rare earth with relative purity less than 99.5%, as well as in a
single rare earth metal and its compounds with other impurity elements greater than
0.5%; it is also not applicable to the determination of the total rare earth content in
materials with individual content of thorium, scandium, and zinc greater than 0.1%.
2 Method-1.Oxalate Gravimetric Method
2.1 Principle of method
After the specimen is decomposed by acid, the rare earth is precipitated in ammonia
water to separate calcium and magnesium.
2.2 Reagents and materials
2.2.1 Perchloric acid (ρ=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).
2.3 Apparatus
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.
2.5.3 Determination
3 Method-2.EDTA Titration Method
3.1 Principle of the method
The testing materials are dissolved in acid; and sulfosalicylic acid is used to mask the
ions e.g., ferric ion, etc. Under the condition of pH 5.5, xylenol orange is used as an
indicator; and use the EDTA standard solution to titrate the rare earth.
3.2 Reagents
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.

Basic Data

Standard ID	GB/T 14635-2020 (GB/T14635-2020)
Description (Translated English)	Rare Earth Metals and Their Compounds - Determination of Total Rare Earth Content
Sector / Industry	National Standard (Recommended)
Classification of Chinese Standard	H14
Word Count Estimation	14,197
Date of Issue	2020-11-19
Date of Implementation	2021-10-01
Older Standard (superseded by this standard)	GB/T 14635-2008
Regulation (derived from)	National Standard Announcement No. 26 of 2020
Issuing agency(ies)	State Administration for Market Regulation, China National Standardization Administration