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

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

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.
GB/T 5750.4-2006
NATIONAL STANDARD OF THE
PEOPLE 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 (??20 = 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 ??m 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 drinking water and its source water.
This method is applicable to the determination of the pH value of drinking water and its source water with very low chroma and turbidity.
Using this method to determine the pH can be accurate to 0.1.
Water samples are colored, turbid, or contain more free residual chlorine, oxidants, reducing agents, it has interference.
5.2.2 Principle
Different acid-base indicators show different colors in a certain pH range. Add the same indicator to a series of standard buffer solutions and water samples with known pH values. Compare the measured pH values of the water samples after color development.
5.2.3 Reagents
5.2.3.1 Potassium hydrogen phthalate solution [c(KHC8H4O4) = 0.10 mol/L]: Place potassium hydrogen phthalate (KHC8H4O4) in an oven at 105 ??C for 2 h and place it in a silica gel dryer to cool it for 30 min. Weigh 20.41 g and dissolve (mol/L);
m - The mass of potassium hydrogen phthalate, in grams (g);
V - The volume of sodium hydroxide solution used for titration of potassium hydrogen phthalate, in milliliters (mL);
V0 - The volume of the sodium hydroxide solution used for titrating the blank solution, in milliliters (mL);
0.2042 - The mass of potassium hydrogen phthalate equivalent to 1.00 mL of sodium hydroxide standard solution [c(NaOH) = 1.000 mol/L].
According to the concentration of the sodium hydroxide stock solution, calculate the volume of the stock solution required to prepare 0.1000 mol/L sodium hydroxide solution according to formula (3). Use pure water to make the volume reach the required value.
Where:
V1 - The volume of the stock solution, in milliliters (mL);
V2 - The volume after dilution, in milliliters (mL);
c1 (NaOH) - Concentration of stock solution.
5.2.3.5 Chlorophenol red indicator: Weigh 100 mg of chlorophenol red
(C19H12C12O5S). Put it in an agate mortar. Add 23.6 mL of sodium hydroxide solution (5.2.3.4). Grind until completely dissolving it. Use pure water to make its volume reach to 250 mL. The applicable pH range of this indicator is 4.8 ~ 6.4.
5.2.3.6 Bromothymol blue indicator: Weigh 100 mg bromothymol blue
(C27H28Br2O5S, also known as thymol blue). Place it in an agate mortar. Add 16.0 mL of sodium hydroxide solution (5.2.3.4). The following operations are the same as (5.2.3.5). The applicable pH range of this indicator is 6.2 ~ 7.6. 5.2.3.7 Phenol red indicator: Weigh 100 mg of phenol red (C19H14O5S). Put it in an agate mortar. Add 28.2 mL of sodium hydroxide solution (5.2.3.4). The following operations are the same as (5.2.3.5). The applicable pH range of this indicator is 6.8 ~ 8.4.
5.2.3.8 Thymol blue indicator: Weigh 100 mg of thymol blue (C27H30O5S, also known as thymol blue). Put it in an agate mortar. Add 21.5 mL of sodium hydroxide solution (5.2.3.4). The following operations are the same as (5.2.3.5). Potassium chloride standard solution [c (KCL) = 0.01000 mol/L]: Weigh 0.7456 g of superior grade pure potassium chloride which had been dried at 110 ??C. Dissolve it in freshly boiled and cooled distilled water (conductivity is less than 1 ??S/cm). Dilute it to 1000 mL in a volumetric flask at 25 ??C. The conductivity of this solution at 25 ??C is 1413 ??S/cm. The solution shall be stored in a plastic bottle.
6.1.4 Instruments
6.1.4.1 Conductivity meter.
6.1.4.2 Constant temperature water bath.
6.1.5 Analytical procedures
6.1.5.1 Pour the potassium chloride standard solution (6.1.3) into 4 test tubes. Then inject the water sample into 2 test tubes. Put 6 test tubes into 25 ??C ?? 0.1 ??C constant temperature water bath at the same time. Heat it for 30 min, to make the temperature of the solution in the tube reach 25 ??C.
6.1.5.2 Use three tubes of potassium chloride solution to rinse the conductivity electrode and conductivity cell in sequence. Then pour the potassium chloride solution in the fourth tube into the conductivity cell. Insert the conductivity electrode to measure the conductivity GKCl or resistance RKCl of potassium chloride.
6.1.5.3 Use one tube of water sample to fully rinse the electrode. Measure the conductivity Gs, or resistance Rs, of the other tube of water sample.
Measure other water samples in turn. If the temperature change is less than 0.2 ??C during the measurement, the conductivity or resistance of the potassium chloride standard solution does not need to be measured again. However, when measuring in different batches (days), it shall measure the conductivity or resistance of potassium chloride solution again.
6.1.6 Calculation
6.1.6.1 Conductivity cell constant C: Equal to the conductivity (1413 ??S/cm) of the potassium chloride standard solution divided by the measured conductivity GKCL of the potassium chloride standard solution. The temperature during measurement shall be 25 ??C ?? 0.1 ??C, then:
6.1.6.2 At 25 ??C ?? 0.1 ??C, the conductivity ?? of water sample is equal to the cell constant C multiplied by the measured conductivity of the water sample (??S) Since the reaction of calcium ion and chrome black T indicator at the end of the titration cannot show a significant color change, so when the magnesium content in the water sample is very small, it needs adding a known amount of magnesium salt to make the color change at the end of the titration clear. When calculating the results, subtract the amount of magnesium salt added, or add a small amount of MgEDTA to the buffer solution, to ensure a clear end point. 7.1.2 Principle
The calcium and magnesium ions in the water sample form a purplish red
chelate with the chrome black T indicator. The instability constants of these chelates are greater than the instability constants of calcium ethylenediamine tetraacetate and magnesium chelates. When pH = 10, disodium
ethylenediaminetetraacetic acid first forms a chelate with calcium ions and then magnesium ions. When titrated to the end, the solution appears pure blue with chrome black T indicator.
7.1.3 Reagents
7.1.3.1 Buffer solution (pH = 10).
7.1.3.1.1 Weigh 16.9 g of ammonium chloride and dissolve it in 143 mL of ammonia water (??20 = 0.88 g/mL).
7.1.3.1.2 Weigh 0.780 g of magnesium sulfate (MgSO4 ?€? 7H2O) and 1.178 g of ethylenediaminetetraacetic acid disodium (Na2EDTA ?€? 2H2O). Dissolve it in 50 mL of pure water. Add 2 mL of chlorination ammonium-amine hydroxide solution (7.1.3.1.1) and 5 drops of chrome black T indicator (the solution shall be purple red. If it is pure blue, a small amount of magnesium sulfate shall be added to make it purple red). Use Na2EDTA standard solution (7.1.3.5) for titration, until the solution changes from purple to pure blue. Combine the solutions of 7.1.3.1.1 and 7.1.3.1.2. Use pure water to dilute it to 250 mL. If the solution turns purple red again after the merger, the reagent blank shall be deducted when calculating the results.
Note 1: This buffer solution shall be stored in polyethylene bottles or rigid glass bottles. The pH value is affected by the ammonia loss due to repeated opening of the plug during use. When the buffer solution is left for a long time and the ammonia concentration decreases, it shall be prepared again.
Note 2: MgEDTA is added when preparing the buffer solution to make the
titration end point of some water samples with lower magnesium content more sensitive. If commercial MgEDTA reagents are available, it may directly weigh 1.25 g of MgEDTA add it to 250 mL buffer solution.
Note 3: When chrome black T is used as an indicator, when titrating calcium and magnesium ions with Na2EDT A, within the pH range of 9.7 ~ 11, the more c (Na2EDTA) - The concentration of Na2EDTA standard solution, in mole per liter (mol/L);
c (Zn) - The concentration of zinc standard solution, in moles per liter (mol/L); V1 - The volume of Na2EDTA solution consumed, in milliliters (mL);
V2 - The volume of the zinc standard solution taken, in milliliters (mL). 7.1.3.6 Chrome black T indicator: Weigh 0.5 g of chrome black T (C20H12O7 N3SNa). Use ethanol [??(C2H5OH) = 95%] to dissolve it. Dilute it to 100 mL. Place it in the refrigerator to preserve it. It can be stable for one month. 7.1.4 Instruments
7.1.4.1 Conical flask, 150 mL.
7.1.4.2 Burette, 10 mL or 25 mL.
7.1.5 Analytical procedures
7.1.5.1 Pipette 50.0 mL of water samples (for water samples with too high hardness, it may take an appropriate amount of water samples, use pure water to dilute it to 50 mL; for water samples with too low hardness, it may take 100 mL). Place it in a 150 mL conical flask.
7.1.5.2 Add 1 mL ~ 2 mL of buffer solution and 5 drops of chrome black T indicator. Immediately use Na2EDTA standard solution to titrate it, until the solution changes from purple red to pure blue. At the same time, carry out a blank test and record the amount consumed.
7.1.5.3 If the water sample contains metal interfering ions, which delays the titration end point or darkens the color, it may take another water sample and add 0.5 mL of hydroxylamine hydrochloride (7.1.3.3) and 1 mL of sodium sulfide solution (7.1.3.2) or 0.5 mL potassium cyanide solution (7.1.3.4); then titrate it. 7.1.5.4 When the bicarbonate content of calcium and magnesium in the water sample is large, it shall first acidify the water sample in advance and heat to remove carbon dioxide, to prevent carbonate precipitation after alkalization, which will affect the progress of the titration reaction.
7.1.5.5 Water samples containing suspended or amine organics may affect the observation of the end point. The water sample may be evaporated to dryness and ashed at 550 ??C in advance; then the residue can be titrated after dissolving the residue in pure water.
7.1.6 Calculation
8.1.2.3 When the total dissolved solids in the water sample contain a large amount of calcium chloride, calcium nitrate, magnesium chloride, magnesium nitrate, the weighing cannot be constant due to the strong hygroscopicity of these compounds. At this time, an appropriate amount of sodium carbonate solution can be added to the water sample to improve it.
8.1.3 Instruments
8.1.3.1 Analytical balance, with a sensitivity of 0.1 mg.
8.1.3.2 Water bath.
8.1.3.3 Electric constant temperature drying oven.
8.1.3.4 Porcelain evaporating dish, 100 mL.
8.1.3.5 Dryer: Use silica gel as desiccant.
8.1.3.6 Medium-speed quantitative filter paper or membrane (pore size 0.45 ??m) and corresponding filters.
8.1.4 Reagents
Sodium carbonate solution (10 g/L): Weigh 10 g of anhydrous sodium
carbonate (Na2CO3). Dissolve it in pure water. Dilute it to 1000 mL.
8.1.5 Analytical procedures
8.1.5.1 Total dissolved solids (bake at 105 ??C ?? 3 ??C)
8.1.5.1.1 Wash the evaporating dish and put it in an oven at 105 ??C ?? 3 ??C for 30 min. Remove and cool in a desiccator for 30 min.
8.1.5.1.2 Weigh it on the analytical balance. Bake and weigh it again, until reaching to a constant mass (the difference between the two weighing does not exceed 0.0004 g).
8.1.5.1.3 Filter the supernatant of the water sample. Use an ungraduated pipette to take 100 mL of the filtered water sample into an evaporating dish. If the total dissolved solids of the water sample are too small, it may increase the sample volume.
8.1.5.1.4 Place the evaporating dish on the water bath and evaporate it dry (the water bath level shall not touch the bottom of the dish). Move the evaporating dish into an oven at 105 ??C ?? 3 ??C. Take it out after 1 h. Cool it in the desiccator for 30 min. Weight it.
8.1.5.1.5 Put the weighed evaporating dish into the 105 ??C ?? 3 ??C oven again and its source water by 4-aminoantipyrine chloroform extraction
spectrophotometry.
This method is applicable to the determination of volatile phenol in drinking water and its source water.
The minimum detection mass of this method is 0.5 ??g volatile phenol
(calculated as phenol). If a 250 mL water sample is taken, the minimum
detection mass concentration is 0.002 mg/L volatile phenol (calculated as phenol).
Reducing sulfides, oxidants, aniline compounds and petroleum in water
interfere with the determination of ph...

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