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GB/T 14635-2008 (GB/T14635-2008)

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GB/T 14635-2008: PDF in English (GBT 14635-2008)
GB/T 14635-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.120.99
H 14
Replacing GB/T 8762.1-1988, GB/T 12687.1-1990,
GB/T 14635.1 ~ 14635.3-1993, GB/T 16484.19-1996, GB/T 18882.1-2002
Rare earth metals and their compounds -
Determination of total rare earth contents
ISSUED ON. JUNE 17, 2008
IMPLEMENTED ON. DECEMBER 01, 2008
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration Committee.
Table of Contents
Foreword ... 3 
Method 1 -- Oxalate gravimetric method ... 6 
1 Scope ... 6 
2 Method principle ... 6 
3 Reagents and materials ... 7 
4 Apparatus ... 7 
5 Specimen ... 7 
6 Analysis steps ... 8 
7 Calculation of analysis results ... 10 
8 Precision ... 11 
Method 2 -- EDTA titration ... 12 
9 Scope ... 12 
10 Method principle ... 13 
11 Reagents ... 13 
12 Specimen ... 14 
13 Analysis steps ... 15 
14 Calculation and expression of analysis results ... 16 
15 Precision ... 19 
16 Quality assurance and control ... 20 
Foreword
This Standard is an integrated revision to GB/T 8762.1-1988 "Yttrium oxide and
europium oxide of phosphor grade - Determination of total rare earth oxide
content - EDTA volumetric method", GB/T 14635.1-1993 "Rare earth metals
and their compounds. Determination of total rare earth contents. Rare earth
oxalate gravimetric method", GB/T 14635.2-1993 "Rare earth metals and their
compounds. Determination of total rare earth contents. EDTA volumetric
method", GB/T 14635.3-1993 "Heavy rare earth metals and their compounds.
Determination of total rare earth contents. EDTA volumetric method", GB/T
16484.19-1996 "Methods for chemical analysis of rare earth chloride and
carbonate - Determination of total rare earth oxide content", GB/T 12687.1-
1990 "Chemical analysis of nitrate of rare earth for agriculture - Determination
of total rare earth oxide content - Gravimetric method", GB/T 18882.1-2002
"Chemical analysis methods for mixed rare earth oxide of ion-absorbed type
RE ore - Determination of total rare earth contents - Oxalate gravimetric
method".
Compared with the above standards that have been integrated for revision, the
main changes in this Standard are as follows.
-- combined GB/T 14635.1-1993, GB/T 16484.19-1996, GB/T 12687.1-1990,
GB/T 18882.1-2002 into Method One;
-- combined GB/T 8762.1-1988, GB/T 14635.2-1993, GB/T 14635.3-1993
into Method Two;
-- in the range for determination in Method One, added individual rare earth
metal and its compounds;
-- in Method One, adjusted the lower determination limit of rare earth
carbonate from 20.0% to 10.0%;
-- in Method One, adjusted the pH2 of acidity of oxalic acid precipitated rare
earth to pH1.8 ~ 2;
-- in Method One, adjusted the burning temperature of rare earth oxide from
1000°C to 950°C;
-- in Method One, modified the way that rare earth carbonate pretreatment is
dried by 105°C TO the way that rare earth carbonate of ionic rare earth
ore is burned at 950°C; other rare earth carbonates are directly weighed
for bulk sample;
-- in Method Two, adjusted the range of determination for rare earth metals
and rare earth oxides from 95.0% ~ 99.5% to 98.0% ~ 99.5%;
Rare earth metals and their compounds -
Determination of total rare earth contents
Method 1 -- Oxalate gravimetric method
1 Scope
This Method specifies the determination method for total rare earth contents in
rare earth metals and their compounds.
This Method is applicable to the determination of total rare earth contents in
individual and mixed rare earth metals and their compounds. See Table 1 for
the range of determination.
This Method is not applicable to the determination of total rare earth contents
in individual and mixed rare earth metals and their compounds of which
holmium, erbium, thulium, ytterbium, lutecium compose the main body or the
thorium content, the lead content (mass fraction) is greater than 0.1%,
respectively.
Table 1
Specimen Range of determination (mass fraction)/%
Rare earth metal 95.0 ~ 99.5
Rare earth oxide 95.0 ~ 99.8
Rare earth hydroxide 55.0 ~ 75.0
Rare earth fluoride 65.0 ~ 80.0
Rare earth chloride 40.0 ~ 60.0
Rare earth carbonate 10.0 ~ 60.0
Rare earth nitrate 30.0 ~ 70.0
Ionic rare earth ore mixed rare earth oxide 80.0 ~ 99.0
2 Method principle
After the specimen is decomposed by acid, precipitate rare earth with ammonia
so as to separate calcium, magnesium, etc. Dissolve rare earth with
hydrochloric acid. Under pH1.8 ~ 2, precipitate rare earth with oxalic acid so as
to separate iron, etc. At 950°C, burn rare earth oxalate into oxide. Weigh its
mass. Calculate the total rare earth contents.
6.3.1.3 Dissolution of rare earth fluoride test material. place the test material
(6.1) into a 200mL beaker. Add 10 mL of nitric acid (3.4), 1 mL of hydrogen
peroxide (3.2) and 3 mL of perchloric acid (3.1). Heat at a low temperature till
perchloric acid smokes. Cool it for a while. Wash the beaker wall with water.
Add 2 mL of perchloric acid (3.1). Heat at a low temperature till perchloric acid
smokes. When the test materials are dissolved completely, evaporate to about
1 mL. Add 20 mL of water. Heat to dissolve the salt till it is clear. Filter. Receive
the filtrate in a 300mL beaker. Wash the beaker and filter with hydrochloric acid
liquid (3.9) 5 ~ 6 times. Discard the filter paper.
6.3.1.4 Dissolution of ionic rare earth ore mixed rare earth oxide, rare earth
carbonate of ionic rare earth ore. place the test material (6.1) into a 300mL
beaker. Add 5 mL of water, 4 mL of hydrochloric acid (3.3), 1 mL of hydrogen
peroxide (3.2), 3 mL of perchloric acid (3.1) [for test material containing high
cerium] as well as 1 mL of hydrogen peroxide (3.2). After separation, add 3 mL
of perchloric acid (3.1). Heat till it dissolves completely. Continue heating till
perchloric acid has white smoke. And evaporate to about 1 mL. Remove. Cool
for a while. Add 20 mL of hydrochloric acid (3.3). Wash the container wall with
hot water. Add 10 mL of water. Heat to dissolve the salt till it is clear. Filter with
quantitative slow filter paper. Receive the filtrate in a 300mL beaker. Wash the
beaker and filter with hydrochloric acid liquid (3.9) 5 ~ 6 times. Wash twice with
hot water. Discard the filter paper.
6.3.1.5 Dissolution of rare earth chloride, rare earth nitrate, rare earth carbonate
(excluding rare earth carbonate of ionic rare earth ore) test materials. place the
test material (6.1) into a 300mL beaker. Add 20 mL of water, 20 mL of
hydrochloric acid (3.3) and 1 mL of hydrogen peroxide (3.2). Heat till it dissolves
completely. Evaporate to about 5 mL [for insoluble test materials, use 20 mL of
nitric acid (3.4) and 2 mL of perchloric acid (3.1) to dissolve]. Add 50 mL of water.
Heat to dissolve the salt till it is clear. Filter. Receive the filtrate in a 200mL
beaker. Wash the beaker and the filter paper with hydrochloric acid liquid (3.9)
5 ~ 6 times. Discard the filter paper. Dilute the filtrate with water to the scale.
Mix evenly. Pipette 10 mL of test solution to a 300mL beaker.
6.3.2 Precipitation separation
6.3.2.1 Dissolute the test solution (6.3.1) with water to about 100 mL. Heat it till
it nearly boils. Add ammonia water (3.5) till precipitate just appears. Add 0.1 mL
of hydrogen peroxide (3.2), 30 mL of ammonia water (3.5). Boil it till it is boiled.
Filter with medium speed quantitative filter paper. Wash the beaker with
ammonium chloride-ammonia liquid (3.7) 2 ~ 3 times. Perform precipitation 6 ~
7 times. Discard the filtrate.
6.3.2.2 Place the precipitate and filter paper in the original beaker. Add 10 mL
of hydrochloric acid (3.3). Crush the filter paper. Add 100 mL of water. Boil it till
it is boiled Add 50 mL of oxalic acid solution (3.6) that is almost boiled. Adjust
pH to 2.0 with ammonia (3.5), hydrochloric acid (3.3) and precision pH test
paper (3.10). Or add 4 ~ 6 drops of cresol red solution (3.11). Adjust with
ammonia (3.5) to make the solution orange (pH 1.8 ~ 2.0). Heat it till it is boiled;
or heat at 80°C ~ 90°C for 40 min. Cool to room temperature. Place for 2h.
6.3.2.3 Filter with slow quantitative filter paper. Wash the beaker with oxalic acid
liquid (3.8) 2 ~ 3 times. Wipe the beaker with a small piece of filter paper.
Transfer all the precipitate to the filter paper. Wash the precipitate 8 ~ 10 times.
Put the precipitate together with the filter paper in the platinum crucible that has
been burnt to constant mass at 950°C. Heat at a low temperature. Perform
ashing for the precipitate and the filter paper.
6.3.2.4 Burn the platinum crucible (6.3.2.3) in a 950°C high-temperature
furnace for 1h. Place the platinum crucible and the finished rare earth oxide into
the dryer. Cool to room temperature. Weigh its mass.
6.3.2.5 Repeat the operation of 6.3.2.4 till it reaches constant weight.
7 Calculation of analysis results
7.1 Calculation and expression of total rare earth contents in rare earth
compound test material
Calculate the total rare earth contents (REO) according to formula (1),
expressed in mass fraction (%).
Where,
m1 - the mass of platinum crucible and burnt material, in grams (g);
m2 - the mass of platinum crucible, in grams (g);
m0 - the mass of test material, in grams (g);
V1 - the volume of divided test solution, in millimeters (mL);
V0 - the volume of original test solution, in millimeters (mL).
7.2 Calculation and expression of total rare earth contents in rare earth
carbonate of ionic rare earth ore test material
Calculate the total rare earth contents (REO) according to formula (2),
expressed in mass fraction (%).
solution (c≈0.02 mol/L).
11.12.1 Preparation. weigh about 15 g of disodium edetate in a 250mL beaker.
Dissolve in small amounts of water. Dissolve with water in a 2L volumetric flask.
Mix evenly.
11.12.2 Calibration. pipette 25.00 mL of zinc standard solution (11.11) into a
250mL flask. Add 50 mL of water, 1 drop of methyl orange indicator (11.9).
Adjust the solution to yellow with ammonia (11.6) and hydrochloric acid (11.4).
Add 5 mL of hexamethylenetetramine buffer solution (11.10), 2 drops of xylenol
orange (11.8). Titrate with EDTA standard titration solution (11.12) until the
solution turns from red to yellow. Perform 3 portions of parallel calibration. The
difference in volume of the EDTA standard titration solution (11.12) consumed
shall not exceed 0.10 mL. Take its average value.
Calculate the actual concentration of the EDTA standard titration solution
according to formula (4).
Where,
c - the actual concentration of EDTA standard titration solution, in molar per
liter (mol/L);
c0 - the concentration of zinc standard solution, in grams per liter (g/L);
V1 - the number of milliliters of divided zinc standard solution, in milliliters
(mL);
V2 - the volume of EDTA standard titration solution consumed by titration of
zinc, in milliliters (mL);
M - the molar mass of zinc, in grams per mole (g/mol).
12 Specimen
12.1 Metal specimen shall be removed from the surface oxide layer. Weigh the
specimen immediately after sampling.
12.2 Burn rare earth oxide at 950°C for 1h. Place it in the dryer. Cool to room
temperature. Weigh immediately.
12.3 For rare earth chloride. crush the specimen. Immediately place it in the
weighing bottle. Weigh immediately.
150mL beaker. Add 5 mL of perchloric acid (11.1), 5 mL of nitric acid (11.3).
Heat it at a low temperature till it is dissolved and it has perchloric acid white
smoke. Cool it for a while. Add 2 mL of perchloric acid (11.1). Cover with a watch
glass. Heat it at a low temperature till it is dissolved and it has perchloric acid
white smoke (if it is not dissolved completely, repeat once). Steam to about 1
mL. Cool. Add 2 mL of hydrochloric acid (11.4). Wash the container wall and
watch glass with water. Dissolve the salt at a low temperature. Transfer the
solution into a 100mL volumetric flask. Dilute with water to scale. Mix evenly.
13.3.1.5 Dissolution of rare earth chloride. place the test material (13.2) in a
300mL beaker. Add 20 mL of water, 10 mL of hydrochloric acid (11.4). Cover
with a watch glass. Heat it at a low temperature till it is dissolved. Cool to room
temperature. Transfer the solution into a 200mL volumetric flask. Dilute with
water to scale. Mix evenly.
13.3.2 Titration
Weigh 10.00 mL of test solution (13.3.1) in a 250mL triangle bottle. Add 50 mL
of water, 0.2 g of ascorbic acid (11.2), 2 mL of sulfosalicylic acid (11.7), 1 drop
of methyl orange (11.9). Adjust the solution to yellow with ammonia (11.6) and
hydrochloric acid (11.4). Add 5 mL of hexamethylenetetramine buffer solution
(11.10), 2 drops of xylenol orange (11.8). Titrate with EDTA standard titration
solution (11.12) until the solution turns from red to yellow.
14 Calculation and expression of analysis results
14.1 Calculation and expression of total rare earth contents in rare earth
compound test material
Calculate the total rare earth contents (REO) according to formula (5), in mass
fraction (%).
Where,
M - the molar mass of rare earth oxides contained in the test material, in
grams per molar (g/mol);
c - the concentration of EDTA standard titration solution, in molars per liter
(mol/L);
V - the volume of EDTA standard titration solution consumed, in milliliters
(mL);
V - the volume of EDTA standard titration solution consumed, in milliliters
(mL);
V1 - the total volume of test solution, in milliliters (mL);
V2 - the volume of divided test solution, in milliliters (mL);
m0 - the mass of test material, in grams (g);
M - 1/x of the molar mass of the mixed oxidized rare earth in which the
relative proportion of rare earth elements is consistent in the test material, in
grams per molar (g/mol); calculated according to formula (8).
Where,
Pi - the mass fraction of each rare earth oxide in the total amount of
corresponding mixed rare earth oxides contained in test material (%);
ki - the molar mass of each rare earth oxide (RExOy), in grams per mole
(g/mol);
x - the number of atoms of rare earth in each rare earth oxide (RExOy)
molecule.
14.4 Calculation and expression of total rare earth contents in mixed rare
earth metal test material of which holmium, erbium, thulium, ytterbium,
lutecium compose the main body
Calculate the total rare earth contents (RE) according to formula (9), in mass
fraction (%).
Where,
c - the concentration of EDTA standard titration solution, in molars per liter
(mol/L);
V - the volume of EDTA standard titration solution consumed, in milliliters
(mL);
V1 - the total volume of test solution, in milliliters (mL);
V2 - the volume of divided test solution, in milliliters (mL);
......
 
(Above excerpt was released on 2018-10-26, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT14635-2008