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GB/T 1873-1995 PDF in English


GB/T 1873-1995 (GB/T1873-1995, GBT 1873-1995, GBT1873-1995)
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GB/T 1873-1995English80 Add to Cart 0-9 seconds. Auto-delivery. Phosphate rock and concentrate. Determination of silicon dioxide content. Gravimetric and volumetric methods  


Standards related to: GB/T 1873-1995

GB/T 1873-1995: PDF in English (GBT 1873-1995)

GB/T 1873-1995
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
Phosphate rock and concentrate - Determination of
silicon dioxide content - Gravimetric and volumetric
methods
APPROVED ON: DECEMBER 20, 1995
IMPLEMENTED ON: AUGUST 01, 1996
Issued by: State Bureau of Technical Supervision
Table of Contents
Foreword ... 3
1 Scope ... 4
2 References ... 4
3 Method summary ... 4
4 Reagents and solutions ... 4
5 Sample ... 5
6 Analysis steps ... 5
7 Expression of analysis results ... 6
8 Allowable difference ... 7
9 Scope ... 7
10 References ... 7
11 Method summary ... 8
12 Reagents and solutions ... 8
13 Sample ... 9
14 Analysis steps ... 9
15 Expression of analysis results ... 10
16 Allowable difference ... 10
Phosphate rock and concentrate - Determination of
silicon dioxide content - Gravimetric and volumetric
methods
Part I -- Perchloric Acid Dehydration Gravimetric Method
(Arbitration Method)
1 Scope
This Standard specifies the determination of silicon dioxide content by
perchloric acid dehydration gravimetric method.
This Standard applies to the determination of silicon dioxide content that is
greater than 1 % in phosphate rock and concentrate products.
2 References
The following standards contain provisions which, through reference in this
Standard, constitute provisions of this Standard. At the time of publication, the
editions indicated are valid. All standards are subject to revision. The parties
who are using this Standard shall explore the possibility of using the latest
version of the following standards.
GB/T 6682-92 Water for laboratory use - Specifications
3 Method summary
The sample is melted with sodium hydroxide, leached with hydrochloric acid.
Perchloric acid is evaporated and smoked to dehydrate the silicic acid. Filter,
burn, and weigh. Desiliconize with hydrofluoric acid. Weigh the residue.
Calculate the silicon dioxide content from its vector.
4 Reagents and solutions
The water used in this Standard shall meet the specifications of Grade 3 water
in GB/T 6682; the reagents listed, unless otherwise specified, refer to analytical
COVER the watch glass, and EVAPORATE to a wet salt form.
6.4 REMOVE the beaker, COOL, ADD 20 mL of hydrochloric acid solution (4.4),
RINSE the watch glass and beaker wall with hot water until the solution volume
is about 50 mL, and HEAT to dissolve the soluble salts. LET IT STAND for a
while, FILTER it with slow quantitative filter paper. First WASH the beaker and
precipitate 4 ~ 6 times with hot hydrochloric acid solution (4.6), then WASH it
with hot water until there are no chloride ions. INSPECT with silver nitrate
solution (4.10).
6.5 PLACE the precipitate together with the filter paper into a platinum crucible.
After careful drying and ashing, PLACE it in a high-temperature furnace and
BURN at 950 °C for 60 min. TAKE OUT and COOL in a desiccator for 30 min,
WEIGH. REPEAT burning for 20 min until the mass is constant.
6.6 ADD several drops of water to the platinum crucible to wet the precipitate,
ADD 3 ~ 5 drops of sulfuric acid solution (4.8) and 3 ~ 5 mL of hydrofluoric acid
(4.9), and slowly HEAT to evaporate to nearly dry. REPEAT the process once
more and continue to HEAT until all white sulfur trioxide smoke is emitted.
PLACE it in a high-temperature furnace and BURN at 950 °C for 60 min. TAKE
OUT and COOL in a desiccator for 30 min, WEIGH. REPEAT burning for 20
min until the mass is constant.
7 Expression of analysis results
The silicon dioxide (SiO2) content (X) expressed in mass percentage is
calculated according to formula (1):
where:
m1 - the mass of precipitation and platinum crucible before hydrofluoric acid
treatment, g;
m2 - the mass of precipitation and platinum crucible after hydrofluoric acid
treatment, g;
m3 - the mass of precipitation and platinum crucible before hydrofluoric acid
treatment of the blank test, g;
m4 - the mass of precipitation and platinum crucible after hydrofluoric acid
treatment of the blank test, g;
m - the mass of the sample, g.
11 Method summary
The sample is melted with sodium hydroxide, leached with water, and acidified.
Add potassium chloride and potassium fluoride to the nitric acid solution to
precipitate silicic acid in the form of potassium fluosilicate. Filter and wash to
remove free acid. Hydrolyze with boiling water to generate hydrofluoric acid.
Use bromothymol phenol blue-phenol red as an indicator. Titrate with sodium
hydroxide standard titration solution. Then the silicon dioxide content can be
determined.
12 Reagents and solutions
The water used in this Standard shall meet the specifications of Grade 3 water
in GB/T 6682; the reagents listed, unless otherwise specified, refer to analytical
reagents.
12.1 Potassium hydroxide (GB/T 2306).
12.2 Hydrochloric acid (GB/T 622).
12.3 Hydrochloric acid solution: 1 + 9.
12.4 Nitric acid (GB/T 626).
12.5 Potassium chloride (GB/T 646).
12.6 Potassium fluoride solution: 200 g/L. WEIGH 40 g of potassium fluoride
(GB/T 1271) and PLACE in a polyethylene beaker, ADD 150 mL of water and
50 mL of nitric acid (12.4), ADD solid potassium chloride (12.5) to saturate,
LEAVE it for 30 min, FILTER with quick filter paper, and STORE the filtrate in a
polyethylene bottle.
12.7 Potassium chloride-ethanol washing solution I: WEIGH 50 g of potassium
chloride (12.5) and DISSOLVE in 800 mL of water and 200 mL of ethanol (GB/T
679), ADD a few drops of 1 g/L methyl red indicator solution, and ADJUST with
sodium hydroxide standard titration solution (4.9) until the color turns yellow.
12.8 Potassium chloride-ethanol washing solution II: WEIGH 50 g of potassium
chloride (4.5) and DISSOLVE in 500 mL of water and 500 mL of ethanol (GB/T
679).
12.9 Sodium hydroxide (GB/T 629) standard titration solution: c(NaOH) = 0.1
mol/L. Preparation and calibration are performed according to GB/T 601.
12.10 Neutral boiling water: ADD a few drops of indicator liquid (12.11) to the
boiling water, and ADJUST with sodium hydroxide standard titration solution
(12.9) until the color turns bright purple.
12.11 Mixed indicator liquid (bromothymol blue-phenol red): WEIGH 0.09 g of
bromothymol blue (HG/T 3-1222) and 0.11 g of phenol red, DISSOLVE in 20
mL of ethanol (GB/T 679) and 20 mL water, ADJUST with sodium hydroxide
standard titration solution (12.9) until the color turns bright purple, and DILUTE
to 100 mL with water.
13 Sample
The sample is passed through a 125 pm test sieve (GB 6003), dried at 105 ~
110 °C for more than 2 h, placed in a desiccator and cooled to room temperature.
14 Analysis steps
14.1 WEIGH 0.1 ~ 0.15 g of sample to the nearest 0.0001 g, PLACE it in a
silver crucible, and ADD 2 g of potassium hydroxide (12.1). CARRY OUT a
blank test at the same time.
14.2 COVER the crucible lid, leaving a gap. PLACE it in a high temperature
furnace, slowly INCREASE the temperature from low temperature to 650 ~
700 °C and keep it for 10 min. TAKE OUT the crucible and turn it, COOL it a
little, PLACE it in a 250 mL polyethylene beaker, ADD 15 ~ 20 mL of boiling
water, and immediately COVER the watch glass. STIR with a polyethylene rod.
WASH the crucible with a small amount of water and hydrochloric acid solution
(12.3), and CONTROL the volume to 30 ~ 40 mL. With constant stirring, quickly
ADD 8 mL of hydrochloric acid (12.2), STIR the solution until it is clear, and
COOL.
NOTE: For samples containing high aluminum, it shall avoid introducing sodium salts to
interfere with the determination. For samples with low aluminum content, it may pipette 25.0
mL of sample solution A prepared from GB/T 1871.1, Part 1, 7.1.1.3 into a 250 mL polyethylene
beaker, and then perform in accordance with 6.3.
14.3 ADD 10 mL of nitric acid (12.4), PLACE the beaker in a cold water bath,
add about 3 g of solid potassium chloride (12.5), and carefully STIR until it is
saturated and there is a small amount of potassium chloride that is not
dissolved. With stirring, slowly ADD 10 mL of potassium fluoride solution (12.6).
Continue stirring for 1 min, and leave it for about 20 min.
14.4 FILTER (or suction filter) using a polyethylene funnel (or wax-coated funnel)
and fast filter paper with filter paper pulp. WASH the beaker and precipitate with
potassium chloride-ethanol washing solution I (12.7) 2 to 3 times each.
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.