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GB/T 6682-1992 PDF in English


GB/T 6682-1992 (GB/T6682-1992, GBT 6682-1992, GBT6682-1992)
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GB/T 6682-1992: PDF in English (GBT 6682-1992)

GB 6682-92 (GB/T 6682-1992)
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
UDC 546.212.542.1
G 04
GB 6682-92
Replacing GB 6682-86
Water for analytical laboratory use –
Specification and test methods
[This standard has been replaced by GB/T 6682-2008]
ISSUED ON. JUNE 29, 1992
IMPLEMENTED ON. MAY 1, 1993
Issued by. National Technical Supervision Bureau
Table of Contents
1 Theme content and application scope . 3 
2 Normative references . 3 
3 Appearance . 3 
4 Classification .. 3 
5 Technical requirements . 4 
6 Sampling and storage . 5 
7 Test methods .. 5 
Annex A (Informative) Reduction formula of conductivity .. 10 
Water for analytical laboratory use –
Specification and test methods
This Standard refers to and adopts International Standard ISO 3696 (1987)
"Water for Analytical Laboratory Use - Specification and Test Methods".
1 Theme content and application scope
This Standard specifies the grade, technical requirements and test methods of
water for analytical laboratory use.
This Standard is applicable to test water for chemical analysis and inorganic
trace analysis. Different grades of water can be used according to actual work
requirements.
2 Normative references
GB 601, Chemical reagent - Preparations of standard volumetric solutions
GB 602, Chemical reagent - Preparations of standard solutions for impurity
GB 603, Chemical reagent - Preparations of reagent solutions for use in test
methods
GB 9724, Chemical reagent - General rule for the determination of pH
GB 9740, Chemical reagent - General method for the determination of dry
residue after evaporation
3 Appearance
Water for analytical laboratory use, with visual observation, shall be colorless
and clear liquid.
4 Classification
Raw water for analytical laboratory use shall be drinking water or water in
proper purity.
The water for analytical laboratory use is divided into three grades. grade 1
6 Sampling and storage
6.1 Container
6.1.1 Water of various grades shall be held in closed and special polyethylene
container. Grade 3 water may be held in closed and special glass container.
6.1.2 New container shall be processed before application through soaking
for 2d~3d with hydrochloric acid solution (mass fraction 20%), repeatedly
washing with to-be-measured water, and filling in to-be-measured water and
soaking more than 6h.
6.2 Sampling
In the case of testing according to this Standard, at least 3L of representative
water sample shall be taken.
Before sampling, the container shall be washed repeatedly with to-be-
measured water; during sampling, the container shall be prevented from being
contaminated. The container shall be full of water sample.
6.3 Storage
During the storage period of water at various grades, the main contamination
sources are soluble constituent of container, carbon dioxide in the air and other
impurities. Therefore, grade 1 water shall not be stored, but prepared before
application. Grade 2 water and grade 3 water may be prepared in the right
amount. They shall be respectively stored in the corresponding containers that
has been washed with the water of same grade in advance.
Water at various grades shall be prevented from being contaminated during the
transportation process.
7 Test methods
In the test methods, each test shall be carried out in the clean environment and
adequate measures shall be taken to prevent the sample from being
contaminated.
Analytical reagent and water of corresponding grade 3shall be used in the test.
7.1 Determination of pH value
100mL of water sample shall be measured out and determined according to the
requirements of GB 9724.
7.2 Determination of conductivity
7.2.1 Instrument
7.2.1.1 Conductivity meter for grade 1 and grade 2 water determination.
equipped with "online" conductivity cell with 0.01cm~0.1cm-1 electrode constant,
have temperature automatic compensation function.
In the case of conductivity meter without temperature compensation function,
"online" heat exchanger may be installed to control the water temperature
25±1°C in the determination; or water temperature may be recorded and
reduced according to Annex A.
7.2.1.2 Conductivity meter for grade 3 water determination. equipped with
conductivity cell with 0.1cm~1cm-1 electrode constant, have temperature
automatic compensation function.
In the case of conductivity meter without temperature compensation function,
thermostatic water-bath groove may be installed to control the to-be-measured
water sample temperature 25±1°C or water temperature may be recorded and
reduced according to Annex A.
7.2.2 Determination procedures
7.2.2.1 Install and trial the instrument according to the instructions of
conductivity meter.
7.2.2.2 Grade 1 and grade 2 water measurement. install the conductivity cell
at the flow water outlet of water treatment unit, adjust the water rate, expel the
gas bubble in the pipe and conductivity cell, and then start measurement.
7.2.2.3 Grade 3 water measurement. take 400mL of water sample to a conical
flask, insert conductivity cell, and then start measurement.
7.2.3 Precautions
Conductivity meter and conductivity cell for measurement shall be calibrated
regularly.
7.3 Test of oxidable substance limit
7.3.1 Reagent
7.3.1.1 Sulfuric acid solution (20%). prepared according to the requirements
of GB 603.
7.3.1.2 Potassium permanganate standard volumetric solution
[c(1/5KMnO4)=0.1mol/L]. prepared according to the requirements of GB 601.
CARRY out reduced pressure evaporation on the water bath (avoiding
evaporate to dryness), STOP heating until the water sample is evaporated to
50mL.
7.5.2.2 Determination
Determine according to GB 9740.
TRANSFER the above pre-contraction water sample INTO a glass evaporation
dish that has been constant-weight at 105±2°C, RINSE the distillation flask with
5mL~10mL of water sample for 2~3 times, COMBINE the washing liquid and
pre-contraction water sample, EVAPORATE on water bath, DRY in the 105±2°C
electric oven to constant-weight. The residue mass must not exceed 1.0 mg.
7.6 Test of soluble silicon limit
7.6.1 Reagents
7.6.1.1 Silicon dioxide standard solution (1mg of SiO2 in 1mL of solution).
prepared according to the requirements of GB 602.
7.6.1.2 Silicon dioxide standard solution (0.01mg of SiO2 in 1mL of solution).
MEASURE 1.00mL of silicon dioxide standard solution (7.6.1.1) into a 100mL
volumetric flask, DILUTE to the scale, SHAKE up, TRANSFER to a
polyethylene bottle, and prepare when needing.
7.6.1.3 Ammonium molybdate solution (50 g/L). WEIGH 5.0g of ammonium
molybdate [(NH4)6Mo7O24·4H2O], DISSOLVE it in water, ADD 20.0mL of sulfuric
acid solution (7.3.1.1), DILUTE to 100mL, SHAKE up, and STORE in a
polyethylene bottle. It shall be discarded if precipitation is discovered.
7.6.1.4 Oxalic acid solution (50 g/L). WEIGH out 5.0g of oxalic acid,
DISSOLVE it in water, DILUTE to 100mL, STORE in a polyethylene bottle.
7.6.1.5 Paramethylaminophenol sulfate (metol) solution (2 g/L). WEIGH out
0.20g of paramethylaminophenol sulfate, DISSOLVE it in water, ADD 20.0g of
sodium metabisulfite, DISSOLVE it, DILUTE to 100mL, SHAKE up, STORE in
a polyethylene bottle. It shall be protected from light. The validity period is two-
week.
7.6.2 Determination procedures
MEASURE out 520mL of grade 1 water (270mL for grade 2 water), POUR into
a platinum dish, CARRY out sub-boiling evaporation to about 20mL under the
dust-proof conditions, STOP heating, COOL down to the room temperature,
ADD 1.0mL of ammonium molybdate solution (7.6.1.3), SHAKE up, PLACE for
5 min, ADD 1.0mL of oxalic acid solution (7.6.1.4), SHAKE up, PLACE for 1 min,
ADD 1.0mL of paramethylaminophenol sulfate solution (7.6.1.5), SHAKE up,
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.