GB/T 5750.4-2006 English PDF (GBT5750.4-2006)

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GB/T 5750.4-2006: Standard examination methods for drinking water -- Organoleptic and physical parameters
GB/T 5750.4-2006
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 13.060
C 51
Partially replacing GB/T 5750-1985
Standard examination methods for drinking water -
Organoleptic and physical parameters
ISSUED ON: DECEMBER 29, 2006
IMPLEMENTED ON: JULY 01, 2007
Issued by: Ministry of Health of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3 
1 Chroma ... 5 
2 Turbidity ... 6 
3 Odor and taste ... 9 
4 Visible substances to the naked eye ... 10 
5 pH ... 10 
6 Conductivity ... 18 
7 Total hardness ... 21 
8 Total dissolved solids ... 25 
9 Volatile phenols ... 27 
10 Anionic synthetic detergent ... 34 
Standard examination methods for drinking water -
Organoleptic and physical parameters
1 Chroma
1.1 Platinum-cobalt standard colorimetry
1.1.1 Scope
This standard stipulates the determination of the chroma of drinking water and
its source water by platinum-cobalt standard colorimetry.
This method is applicable to the determination of the chroma of drinking water
and its source water.
The water sample is not diluted. The minimum detection chroma of this method
is 5 degrees. The measurement range is 5 degrees ~ 50 degrees.
The suspended matter in the water sample shall be removed before the
measurement.
1.1.2 Principle
The potassium chloroplatinate and cobalt chloride are used to prepare a
standard color series similar to the natural water’s yellow hue, which is used for
the visual colorimetric determination of water samples. The color of 1 mg/L
platinum [existed in the form of (PtCl6)2- is specified as a color unit, which is
called 1 degree. Even slight turbidity can interfere with the measurement, so
the turbid water sample needs to be centrifuged to make it clear before
measurement.
1.1.3 Reagents
Platinum-cobalt standard solution: Weigh 1.246 g of potassium chloroplatinate
(K2PtCl6) and 10.00 g of dry cobalt chloride (CoCl2 • 6H2O). Dissolve it in 100
mL of pure water. Add 100 mL of hydrochloric acid (ρ20 = 1.19 g/mL). Use pure
water to make the volume reach to 1000 mL. The chroma of this standard
solution is 500 degrees.
1.1.4 Instruments
1.1.4.1 Complete set of high-grade colorless plugged colorimetric tubes, 50 mL.
The minimum detection turbidity of this method is 0.5 nephelometric turbidity
unit (NTU).
Turbidity is an indicator that reflects the physical characteristics of water source
and drinking water. The turbidity of the source water is caused by optical
scattering or absorption behavior due to suspended solids or colloidal
substances, or both.
2.1.2 Principle
Under the same conditions, the intensity of the scattered light of the Formazine
standard suspension is compared with the intensity of scattered light of the
water sample. The greater the intensity of the scattered light, the higher the
turbidity.
2.1.3 Reagents
2.1.3.1 Pure water: Take distilled water and filter through a 0.2 μm membrane
filter.
2.1.3.2 Hydrazine sulfate solution (10 g/L): Weigh 1.000 g of hydrazine sulfate
[(NH2)2 • H2SO4, also known as hydrazine sulfate]. Dissolve it in pure water and
make its volume reach to the mark in a 100 mL volumetric flask.
Note: Hydrazine sulfate is carcinogenic. Avoid inhalation, ingestion, or
skin contact!
2.1.3.3 Cyclo-hexamethylenetetramine solution (100 g/L): Weigh 10.00 g of
cyclo-hexamethylenetetramine [(CH2)6N4]. Dissolve it in pure water and make
its volume reach to the mark in a 100 mL volumetric flask.
2.1.3.4 Standard suspension of Formazine: Respectively pipette 5.00 mL of
hydrazine sulfate solution and 5.00 mL of cyclo-hexamethylenetetramine
solution in a 100 mL volumetric flask. Mix it uniformly. After placing at 25 °C ±
3 °C for 24 h. Add pure water to the mark and mix it uniformly. This standard
suspension has a turbidity of 400 NTU and can be used for about one month.
2.1.3.5 Formazine turbidity standard use solution: Use pure water to dilute the
Formazine turbidity standard suspension (2.1.3.4) 10 times. The turbidity of this
suspension is 40 NTU. It shall be appropriately diluted during use according to
the need.
2.1.4 Instruments
Scattering turbidity meter.
2.1.5 Analytical procedures
5.1.1 Scope
This standard specifies the determination of the pH value of domestic drinking
water and its source water by the glass electrode method.
This method is applicable to the determination of the pH value of domestic
drinking water and its source water.
The pH value determined by this method can be accurate to 0.01.
The pH value is the logarithm of the reciprocal of hydrogen ion’s activity in water.
The chroma, turbidity, free chlorine, oxidant, reducing agent, higher salt content
of water does not interfere with the measurement. However, in a strong alkaline
solution, when a large amount of sodium ions is present, an error will occur,
which will make the reading relatively low.
5.1.2 Principle
The glass electrode is used as the indicator electrode, the saturated calomel
electrode is used as the reference electrode, which are inserted into the solution
to form a primary battery. When the hydrogen ion’s concentration changes, the
electromotive force between the glass electrode and the calomel electrode also
changes. At 25 °C, each unit of the pH scale is equivalent to 59.1 mV
electromotive force’s change, directly represented by the pH reading on the
instrument. There is a temperature difference compensation device on the
instrument.
5.1.3 Reagents
5.1.3.1 Potassium hydrogen phthalate standard buffer solution: Weigh 10.21 g
of potassium hydrogen phthalate (KHC8H4O4) which had been dried at 105 °C
for 2 h. Dissolve it in pure water and dilute to 1000 mL. The pH value of this
solution is 4.00 at 20 °C.
5.1.3.2 Mixed phosphate standard buffer solution: Weigh 3.40 g of potassium
dihydrogen phosphate (KH2PO4) which had been dried at 105 °C for 2 h and
3.55 g of disodium hydrogen phosphate (Na2HPO4). Dissolve it in pure water
and dilute it to 1000 mL. The pH of this solution is 6.88 at 20 °C.
5.1.3.3 Sodium tetraborate standard buffer solution: Weigh 3.81 g of sodium
tetraborate (Na2B4O7 • 10H2O). Dissolve it in pure water. Dilute it to 1000 mL.
The pH value of this solution is 9.22 at 20 °C.
mixed phosphate standard buffer solution for repositioning. If the water
sample’s pH is > 7.0, use sodium tetraborate standard buffer solution for
positioning; use potassium bi-phthalate or mixed phosphate standard buffer
solution for repositioning.
Note: If the positioning values of the three buffers are found to be non-linear, it
shall check the quality of the glass electrode.
5.1.5.4 Use the washing bottle to slowly rinse the two electrodes several times
by pure water. Then use water sample to rinse it for 6 ~ 8 times. Then insert it
into the water sample. After 1 min, directly read the pH value from the
instrument.
Note 1: In the calomel electrode, it is a saturated solution of potassium chloride.
When the room temperature rises, the solution may change from a saturated
state to an unsaturated state, so a certain amount of potassium chloride crystals
shall be maintained.
Note 2: For solutions with a pH value greater than 9, the pH value shall be
measured using a high-alkali glass electrode.
5.2 Standard buffer solution colorimetry
5.2.1 Scope
This standard specifies the standard buffer solution colorimetric method for
measuring the pH of ...