YS/T 575.21-2007 English PDF (YST575.21-2007)

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YS/T 575.21-2007: Methods for chemical analysis of bauxite. Part 21: Determination of organic carbon content. Titrimetric method
YS/T 575.21-2007
YS
NONFERROUS METALS INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 71.100.10
Q 52
Replacing YS/T 575.21-2006
Methods for Chemical Analysis of Bauxite - Part 21:
Determination of Organic Carbon Content - Titrimetric
Method
ISSUED ON: NOVEMBER 14, 2007
IMPLEMENTED ON: MAY 01, 2008
Issued by: National Development and Reform Commission
Table of Contents
Foreword ... 3
1 Scope ... 6
2 Method Principle ... 6
3 Reagents ... 6
4 Determination Device ... 7
5 Specimen ... 8
6 Analysis Procedures ... 8
7 Calculation of Analysis Results ... 9
8 Precision ... 10
9 Quality Assurance and Control ... 10
Methods for Chemical Analysis of Bauxite - Part 21:
Determination of Organic Carbon Content - Titrimetric
Method
1 Scope
This Part specifies the determination method of organic carbon content in bauxite.
This Part applies to the determination of organic carbon content in bauxite.
Determination range: 0.01% ~ 1.00%.
2 Method Principle
After boiling and decomposing carbonate by phosphoric acid, use silver sulfate as a
catalyst. Use potassium persulfate to oxidize the carbon in the organic matter to carbon
dioxide; and then use thymolphthalein as an indicator; then use ethanol-ethanolamine-
potassium hydroxide solution to absorb and titrate.
3 Reagents
3.1 Silver sulfate.
3.2 Phosphoric acid (1+1).
3.3 Saturated aqueous solution of potassium persulfate.
3.4 Sodium oxalate standard solution: take 0.2000g of sodium oxalate (reference
substance) that has been dried at 130°C in advance; dissolve it by water; transfer it to
a 200mL volumetric flask; dilute to the mark with water; and shake it well. 1mL of this
solution contains 1mg of sodium oxalate.
3.5 Ethanol-ethanolamine absorption solution: mix evenly 900mL of absolute ethanol
with 100 mL of ethanolamine; and add 0.1g of thymolphthalein to mix evenly.
3.6 Ethanol-ethanolamine-potassium hydroxide standard titration solution: dissolve
1.3g of potassium hydroxide in 900mL of absolute ethanol; stand for one day; filter out
the insoluble matter. Add 100mL of ethanolamine and 0.1g of thymolphthalein indicator;
mix evenly. The concentration of the solution is determined in accordance with sub-
8 - Condensing tube;
9 - Three-necked flask, 500mL;
10 - Electric furnace;
11 - Separating funnel, 100mL;
13 - Gas scrubber, containing 20% copper sulfate;
16 - Absorption cup, containing absorption solution;
17 - Reference cup, containing absorption solution;
18 - Burette.
Figure 1 – Determination Device
5 Specimen
Grind the specimen by a mortar to pass through a 71μm sieve; dry the ground
specimen at 110°C±5°C for 2h; place it in a desiccator; and cool to room temperature
for later use.
6 Analysis Procedures
6.1 The number of determinations
The same specimen shall be determined for twice independently and the average
value shall be taken.
6.2 Blank test
Do a blank test with the testing material.
6.3 Connect the determination device according to the diagram of the determination
device; add ethanol-ethanolamine absorption solution (3.5) to the absorption cup and
the reference cup, respectively; so that the liquid level of the solution is 2cm~4cm
above the sieve plate in the cup. Ventilate (control the flowrate to about 0.3L/min); use
ethanol-ethanolamine-potassium hydroxide standard titration solution (3.6) to titrate
until the solution is stable blue (the color in the absorption cup is the same as the
reference cup); stop ventilation.
6.4 Remove the carbonate in the specimen and the carbon dioxide in the system