GB/T 1819.2-2004 English PDF (GBT1819.2-2004)

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GB/T 1819.2-2004: Methods for chemical analysis of tin concentrates -- Determination of tin content -- The potassium iodate titrimetric method
GB/T 1819.2-2004
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 73.060
D 41
Replacing GB/T 1820-1979
Method for chemical analysis of tin concentrates -
Determination of tin content - The potassium iodate
titrimetric method
ISSUED ON: FEBRUARY 05, 2004
IMPLEMENTED ON: JULY 01, 2004
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Principles of the method ... 4 
3 Reagents ... 4 
4 Reduction device (see Figure 1) ... 6 
5 Specimen ... 6 
6 Analytical procedures ... 7 
7 Calculation of analysis results ... 8 
8 Precision ... 9 
Method for chemical analysis of tin concentrates -
Determination of tin content - The potassium iodate
titrimetric method
1 Scope
This standard specifies the determination method of tin content, in tin
concentrate.
This standard applies to the determination of the tin content, in tin concentrate.
Measuring range: >30.00%.
2 Principles of the method
The sample is decomposed by hydrochloric acid and potassium chlorate.
Arsenic is volatilized in the form of chloride. In the presence of disodium
ethylenediaminetetraacetic acid, beryllium hydroxide is used as a carrier; tin is
precipitated with ammonia water, to separate it from copper, tungsten, antimony,
bismuth and other elements. It is ashed and precipitated, melted with zinc
powder-borax-boric acid, leached with hydrochloric acid; then the tin is reduced
to divalent, with iron powder and aluminum powder. Using starch as an indicator,
use potassium iodate standard titration solution, to titrate the test solution, to
light blue, which is used as the end point.
3 Reagents
3.1 Zinc powder (industrial pure, particle size 0.074 ~ 0.18 mm).
3.2 Reduced iron powder.
3.3 Aluminum powder (> 99.5%).
3.4 Potassium chlorate.
3.5 Hydrazine sulfate.
3.6 Potassium bromide.
3.7 Borax (Na2B4O7).
3.8 Boric acid.
3.9 Sodium chloride.
3.10 Sodium hydroxide.
3.11 Hydrochloric acid (ρ 1.19 g/mL).
3.12 Hydrogen peroxide (30%).
3.13 Ammonia (ρ 0.90 g/mL).
3.14 Zinc powder-borax-boric acid mixed flux: Take 20 g of borax and 10 g of
boric acid. Grind it in a mortar. Add 90 g of industrial zinc powder. Mix well. Put
it in a porcelain dish. Place it in an oven, at 100 ~ 105 °C, to bake it for 1 hour.
Take it out. Grind it after cooling. Put it into a bottle. Keep it sealed.
3.15 Hydrochloric acid solution [c(HCl) = 6.5 mol/L].
3.16 Disodium ethylenediaminetetraacetic acid (Na2EDTA) solution (100 g/L).
3.17 Beryllium sulfate (BeSO4 • 4H2O) solution (40 g/L).
3.18 Ammonia-nitric acid washing solution: 1 g of ammonium nitrate is
dissolved into 100 mL of ammonia (1 + 99).
3.19 Potassium iodide solution (100 g/L).
3.20 Potassium iodide standard titration solution [c(1/6KIO3) = 5 x 10-5 mol/mL]
3. 20.1 Preparation; Weigh 1.8 g of potassium iodate, 9 g of potassium iodide,
0.3 g of sodium hydroxide. Place them in a 500 mL beaker. Add 200 mL of water.
Heat until it is completely dissolved. Use glass wool, to filter the solution into a
1000 mL volumetric flask. Use water to dilute it to the mark. Mix well.
3.20.2 Calibration: Weigh three sets of 0.1200 g metallic tin (99.99%). Put them
in a 300 mL conical flask. Do a blank test together. Add 1 g of reducing iron
powder, 80 mL of hydrochloric acid solution (3.15). Heat it at low temperature,
to dissolve completely. Add 20 mL of water. Proceed calibration according to
6.4.5 ~ 6.4.6.
Calculate the actual concentration of potassium iodate standard titration
solution, according to formula (1):
Where:
c - The actual concentration of potassium iodate standard titration solution,
5.2 The specimen shall be dried in an oven, at 105°C ± 5°C for 1 h. Then it is
placed in a desiccator, to cool to room temperature, for later use.
6 Analytical procedures
6.1 Sample
Weigh a 0.2 g of specimen, accurate to 0.0001 g.
6.2 Number of determinations
Perform 2 measurements independently. Take the average value.
6.3 Blank test
Do a blank test with the sample.
6.4 Determination
6.4.1 Place the sample (6.1) in a 250 mL beaker. Add 2 g of potassium chlorate,
20 mL of hydrochloric acid (3.11). Heat to decompose for 20 min, at low
temperature.
6.4.2 Add 60 mL of hydrochloric acid (3.15), 1 g of hydrazine sulfate, 0.3 g of
potassium bromide. Heat and evaporate for more than 50 minutes. During the
evaporation process, add hydrochloric acid (3.15), to keep the volume at about
30 mL. Take it down and cool it slightly. Cover a watch glass. Add hydrogen
peroxide dropwise, until a brownish-red bromine gas appears. Add 10 mL of
EDTA solution, 5 mL of beryllium sulfate solution. Use ammonia to neutralize it,
to pH9 ~ 10. Use a slow filter paper, which has a little pulp, to filter it. Use
ammonia water-ammonium nitrate lotion, to wash the precipitate 7 ~ 8 times.
Use a glass rod, which has a rubber head, to carefully scrub the beaker, to
transfer all the precipitate to the filter paper. Then move the precipitate together
with the filter paper, into a 5 mL tall corundum crucible (or porcelain crucible).
Dry it. Ash it. Cool it down.
Note: When the sample contains less than 10 mg of arsenic, less than 1 mg of copper,
less than 10 mg of tungsten trioxide, less than 2.5 mg of antimony, it may omit the
operation of 6.4.1 ~ 6.4.2. It may directly put the sample (6.1) in a 5 mL crucible, which
contains 2 g of mixed flux. Follow the operations of 6.4.3 ~ 6.4.6 below.
6.4.3 Add 2 g of zinc powder-borax-boric acid mixed flux to the crucible. Use a
thin glass rod to stir it carefully. Use a small brush, to clean the thin glass rod.
Cover with 1 g of mixed flux. Cover with 1 g of sodium chloride. Move it in a
box-type resistance furnace, which has been heated to 750 °C. Heat to 820 °C,
to melt it for 30 minutes. Take it out. Cool it down.