This standard specifies the measurement method of dissolved oxygen concentration in industrial circulating cooling water. This standard is applicable to the determination of dissolved oxygen concentration in industrial circulating water of 0.2 to 8 mg/L (in terms of O 2). GB/T 15455-1995 Determination of dissolved oxygen in industrial circulating cooling water Iodometric method GB/T15455-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of dissolved oxygen in industrial circulating cooling water
Iodometric method
Industrial circulating cooling water-Determinationof dissolved oxygen- odimetryThis standard refers to and adopts the international standard 1SO5813-1983 "Determination of dissolved oxygen in water quality—1 Subject content write Scope of application
This standard specifies the measurement method for dissolved oxygen content in industrial circulating cooling water. GB/T1545595
Iodometric method".
This standard is applicable to the determination of dissolved oxygen concentration in industrial circulating water of 0.2~8mg/L (measured in O2). 2 Reference standards
GB/T602 Preparation of standard solution for determination of impurities in chemical reagents GB/T6682 Specifications and test methods for water used in analytical laboratories 3 Summary of methods
The determination of dissolved oxygen adopts the manganese salt iodine method, the principle of which is: in alkaline solution, divalent manganese ions are oxidized to trivalent or tetravalent manganese by oxygen dissolved in water. The dissolved oxygen can be fixed:
Mn2++2OH2 Mn(OH)2→
2Mn(OH), +O, -- 2H2MnO: +
4Mn(OH),+O,+2H,0-4Mn(OH),
Then the solution is acidified, and potassium iodide is added, and the trivalent or tetravalent manganese is reduced to divalent manganese ions, and iodine with the same amount of substance as dissolved oxygen is generated.
HzMnO:+4H++21~-Mn2++I2+3HO
2Mn(OH):+6H++21--12+6H20+2Mn2+Use sodium thiosulfate standard titration solution to titrate the generated iodine to obtain the dissolved oxygen in the water. 4 Reagents and Materials
In the analysis method, unless otherwise specified, analytical reagents and the specifications of grade 3 water in GB/T6682 should be used. The standard push solution required for the analysis shall be prepared in accordance with the provisions of GB/T602 unless otherwise specified. 4.1 Sulfuric acid (GB/T625): 1+1 solution.
4.2 Sulfuric acid (GB/T625): 1+17 solution.
4.3 Manganese sulfate (HG/T3-1081) solution: 340g/L Weigh 34 manganese sulfate, add 1m sulfuric acid solution (4.1), dissolve, dilute with water to 100mL, if the solution is not clear, filter. 4.4 Alkaline potassium iodide mixture:
Weigh 30g sodium oxide (GB/T629), 20g potassium iodide (GB/T1272) and dissolve in 100mL water, shake well. Approved by the State Administration of Technical Supervision on January 12, 1995, implemented on October 1, 1995
4.5 Starch solution: 10g/L, freshly prepared. GB/T15455-95
4.6 Potassium iodate (GB/T651) standard solution: c(1/6KIO.)=0.01000mol/L. Weigh 3.567g potassium iodate dried at 180℃, accurate to 0.002g, and dissolve in water, transfer to a 1000mL volumetric flask, dilute to scale, and shake well.
Pipette 100.0mL into a 1000mL volumetric flask, dilute to scale with water, and shake well. 4.7 Sodium thiosulfate standard titration solution: c(NazS2O;) = 0.01mol/L. 4.7.1 Dissolve 2.50g sodium thiosulfate (GB/T637) in freshly boiled and cooled water, add 0.4g sodium hydroxide (GB/T629), and dilute to 1000mL with water. Store in a brown glass bottle. Calibrate after 15 to 20 days. 4.7.2 Calibration: Pipette 25.00 mL of diluted potassium iodate solution (4.6) into a conical flask, add about 100 mL of water, 0.5 g of potassium iodide, and 5 mL of sulfuric acid solution (4.2). Titrate with sodium thiosulfate standard titration solution (4.6). When a light yellow color appears, add starch indicator (4.5). Titrate until the blue color disappears completely. Calculate the concentration of sodium thiosulfate standard titration solution. 4.8 Potassium permanganate (GB/T643) solution: c(1/5KMnO) = 0.01 mol/L. 4.9 Potassium aluminum sulfate (GB/T1275) solution: 100 g/L. 4.10 Sampling bottle: Two stoppered glass bottles, measure the volume of water contained when stoppered. One bottle is called A and the other is called B. The volume requirement is 200~500 mL.
5 Analysis stepswwW.bzxz.Net
5.1 Sampling
Put the cleaned sampling bottles A and B (4.10) in a cleaned sampling bucket at the same time. The sampling bucket should be at least 15 cm higher than the sampling bottles. Two cleaned polyethylene plastic tubes or inert material tubes are inserted into the bottom of sampling bottles A and B respectively. Use siphon or other methods to introduce water samples into sampling bottles A and B through the catheter at the same time. The flow rate is preferably about 700 mL/min. And let the water naturally overflow from bottles A and B into the bucket until the water level in the sampling bucket is more than 15 cm higher than the mouth of sampling bottles A and B. 5.2 Pretreatment of water samples
If there are suspended substances that can fix or consume oxygen in the water sample, potassium aluminum sulfate solution (4.9) can be used for flocculation: fill a 1000 mL stoppered bottle with the water sample to be tested and let the water overflow (such as the sampling process in 5.1). Transfer 20mL of potassium aluminum sulfate solution (4.9) and 4mL of ammonia water (GB631) to the water sample to be tested. Add a stopper, mix well, and let it stand to settle. Pipette the upper clear liquid into a narrow-necked bottle, and then analyze according to the determination steps. 5.3 Fixed oxygen and acidification
Use a thin glass tube to absorb about 1mL of manganese sulfate solution (4.3). Insert the glass tube into the middle of bottle A and put in manganese sulfate solution. Then add 5mL of alkaline potassium iodide mixed solution (4.4) in the same way. 2.00mL of potassium permanganate standard solution (4.8), place bottle A under the water layer of the sampling bucket, wait for the precipitation in bottle A, open the bottle stopper underwater, and then add 5mL of sulfuric acid solution (4.1) to bottle A, cover the bottle stopper tightly, take out and shake well. First add 5mL sulfuric acid solution (4.1) to bottle B, then add about 1mL manganese sulfate solution (4.3), 5mL alkaline potassium iodide mixture (4.4), and 2.00mL potassium permanganate standard solution (4.8) at the same place where sulfuric acid was added. No precipitation should be produced. Otherwise, retest. Close the bottle stopper, take it out, shake it well, and place bottle B under the water layer of the sampling bucket. 5.4 Determination
Pour the solutions in bottles A and B into two 600mL or 1000mL beakers respectively, and titrate with sodium thiosulfate standard titration solution (4.7) until it turns light yellow, add 1mL starch solution (4.5) and continue titrating. The solution changes from blue to colorless. Rinse the original bottles A and B with the titrated solution, and continue titrating until it is colorless.
6 Expression of analysis results
6.1 The content of dissolved oxygen in the water sample expressed in mg/I (in terms of O2) is calculated according to formula (1): /0.008×/.c_ 0.008×V:-9)×10r=
Wherein: c-concentration of sodium thiosulfate standard titration solution, mol/L; 550
VB— VB
GB/T15455-95
V,-—volume of sodium thiosulfate standard titration solution consumed in titrating the water sample in bottle A, mL; VA-——capacity of bottle A, mL;
VA-——the sum of the volumes of manganese sulfate solution, alkaline potassium iodide mixture, sulfuric acid and potassium permanganate solution added to bottle A, mL; V---B Volume of bottle, mL;
V2---Volume of sodium thiosulfate standard titration solution consumed in titrating bottle B water sample, mL; Ve---The sum of the volumes of manganese sulfate solution, alkaline potassium iodide mixture, sulfuric acid and potassium permanganate solution added to bottle B, mL; 0.008---The mass of oxygen equivalent to 1.00mL sodium thiosulfate standard titration solution [c(NazS,Og)1.000 mol/L], expressed in grams.
6.2 If the water sample is pretreated, the dissolved oxygen content in the water sample expressed in mg/L (in O,) z2 ​​is calculated according to formula (2): (2)
Where: V--The actual volume of the 1000mL stoppered bottle in 5.2, mL; Vi--Volume of potassium aluminum sulfate solution and ammonia water, mL; z1-The value calculated by formula (1), mg/L. 7 Allowable difference
The arithmetic mean of the parallel determination results is taken as the determination result. The relative deviation of the parallel determination results shall not exceed 2%. The relative deviation of the determination results between laboratories shall not exceed 3%. Additional remarks:
This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China. This standard is under the technical supervision of Tianjin Chemical Industry Research Institute of the Ministry of Chemical Industry. This standard is drafted by Nanjing Institute of Chemical Technology. The main drafters of this standard are Yu Bin and Yu Minghua. 551
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