HG/T 2158-1991 Determination of ammonium in industrial circulating cooling water by distillation and titration HG/T2158-1991 Standard download decompression password: www.bzxz.net

Chemical Industry Standard of the People's Republic of China
Determination of ammonium in industrial circulating cooling water
Distillation and titration method
HG/T2158-91
This standard refers to the international standard ISO5664-84 "Water quality-Determination of ammonium-Distillation and titration method". 1 Subject content and scope of application
This standard specifies the determination of the total content of ammonium in industrial circulating cooling water by distillation and titration. This standard is applicable to the determination of ammonium (in terms of N) in industrial circulating cooling water with a content of 0.50~100.0mg/L. 2 Reference standards
Chemical reagents, preparation of standard solutions for titration analysis (volumetric analysis) GB601
GB603 Preparation of preparations and products used in chemical reagent test methods 3 Method summary
Adjust the pH of the water sample to about 7.4. Add manganese dioxide to make the water sample slightly alkaline, heat and distill, collect the distilled ammonia in the absorption solution containing boric acid and methyl red-methylene blue mixed indicator, and titrate the ammonium in the absorption solution with hydrochloric acid standard titration solution. 4 Reagents and Materials
In the analytical method, unless otherwise specified, only analytically pure reagents and water that meets the requirements of 4.1 should be used. 4.1 Water: The water should be free of ammonium and prepared by one of the following methods. 4.1.1 Ion exchange method: Distilled water passes through a column of strong acid cation exchange resin (hydrogen type), and the effluent water is collected in a glass bottle equipped with a sealed ground stopper. About 10g of the same resin is added to each liter of effluent water to facilitate storage. 4.1.2 Distillation method: Pipette 0.1mL sulfuric acid (GB625) into 1000mL distilled water, and then distill again in a full glass apparatus, discard the first 50mL of distilled water, and then collect the distilled water in a glass bottle equipped with a sealed ground stopper, and add about 10g of strong acid cation exchange resin (hydrogen type) per liter of distilled water. 4.2 Hydrochloric acid (GB622) standard titration solution: c(HCl) = 0.1000mol/L standard titration solution. 4.3 Hydrochloric acid (GB622) standard titration solution: c(HCI) = 0.02mol/L standard titration solution; pipette 100.0mL hydrochloric acid standard titration solution (4.2) into a 500mL volumetric flask, dilute to the mark with water (4.1), and shake well. 4.4 Boric acid-indicator solution
4.4.1 Dissolve 0.20 g methyl red (HG3-958) in 95 mL ethanol (GB978) and 5 mL water (4.1), mix well
4.4.2 Dissolve 0.20 g methylene blue (HGB3394) in 95 mL ethanol (GB978) and 5 mL water (4.1), mix well
4.4.3 Dissolve 20% boric acid (GB628) in 30~40°C warm water (4.1), cool to room temperature, add 7.0 mL methyl red solution (4.4.1) and 3.5 mL methylene blue solution (4.4.2), and dilute with water (4.1). Dilute to 100.0mL, mix well.4.5 Bromothymol blue (bromothymol blue) (HG3-1222) solution: 0.5g/L Approved by the Ministry of Chemical Industry of the People's Republic of China on September 16, 1991 and implemented on January 1, 1992
HG/T2158--91
4.6 Hydrochloric acid (GB622) solution: 1% (V/V).4.7 Sodium hydroxide (GB629) solution: 40g/L4.8 Manganese dioxide: Put manganese dioxide in a 50㎡L porcelain pot, put it in a high-temperature furnace (5.7) and heat it at 500℃ for about 2h to remove carbonate, take it out, cool it to room temperature, and immediately store it in a glass bottle.4.9 Glass ball: diameter 1~3mm.
5 Instruments and Equipment
Diagram of distillation apparatus for ammonium
5.1 Distillation apparatus: Connect the 500mL long-necked distillation round-bottom flask (5.2) with the double-connected nitrogen balls (5.5) and the straight condenser (5.6) according to the diagram, so that the outlet of the condenser can be immersed in the conical flask (5.3) containing the absorption liquid. All joints must be sealed and leak-proof, and then heated with an electric furnace (5.4).
5.2 Long-necked round-bottom flask: 500mL;
5.3 Conical flask: 300mL;
5.4 Electric furnace: 1kW;
5.5 Double-connected nitrogen balls;
5.6 Straight condenser: 400mm long;
5.7 High-temperature furnace: 3kW.
6 Sampling
6.1 The sampling bottle should be a polyethylene or glass narrow-necked bottle with a threaded cap. After cleaning with detergent, rinse with water (4.1). 6.2 In an open circulating cooling water system, sampling is usually done in the return pipe before entering the cooling tower; in a direct current water system, sampling is done at the outlet pipe; in a sealed closed-circuit system, sampling is done at a low position. 6.3 To ensure that the sampling is representative, all parts of the pipeline should be kept full of water. Before formal sampling, drain some of the water first, then take out the sample from the jade pipe to clean the sampling bottle. Finally, after filling the sampling bottle with the sample, tighten the cap and analyze it as soon as possible. Otherwise, it should be stored at 2~5℃ for about 6h.
7 Analysis steps
7.1 Sample
HG/T2158-91
If the approximate ammonium content in the sample is known, the sample volume can be selected according to Table 1. Table 1 Selection of sample volume
Ammonium concentration (in N), mg/L
50~100
7.2 Pre-cleaning of distillation apparatus
Sample volume, mL
7.2.1 Between two determinations, when the distillation is completed and the absorption conical flask (5.3) is removed, the residual liquid in the long-necked round-bottom flask should be distilled to leave about 50 mL before the next determination can be carried out; whenever the apparatus is out of use for more than one day or is just being used, it should be pre-cleaned according to the procedure in 7.2.2.
7.2.2 Add about 350 mL of water (4.1) to a 500 mL long-necked round-bottom flask, add a few glass balls (4.9), and connect the distillation apparatus as shown in the figure. Heat and distill until there is at least 100 mL of distillate. Remove the conical flask and discard the water and the residual liquid in the round-bottom flask. 7.3 Determination
7.3.1 Add 50 mL of boric acid-indicator solution (4.4) to the conical flask (5.3) of the distillation apparatus, ensuring that the lower end of the condenser is lower than the liquid level of the boric acid solution (4.4). Use a pipette to draw the selected volume of sample (7.1) and add it to the long-necked round-bottom flask. Then add water (4.1) to make the total volume of the solution in the long-necked round-bottom flask reach 350mL. Add 4 to 5 drops of bromothymol blue indicator solution (4.5). If the solution is light yellow (pH < 6), add sodium hydroxide (4.7) until the solution just turns blue (pH > 7.4). If the solution is light blue (pH > 7.4), add hydrochloric acid (4.3) until the solution just turns light yellow, and then add sodium hydroxide (4.7) until the solution just turns light blue. 7.3.2 Add 0.25g of manganese dioxide (4.8) and several glass balls (4.9) to the long-necked round-bottom flask, and immediately connect the round-bottom flask as shown in the figure.
7.3.3 Heat the distillation to make the distillate distill at about 5~10mL/min. When about 200mL is collected, remove the conical flask (5.3) and stop steaming the stuffing.
7.3.4 Titrate the distillate with hydrochloric acid standard titration solution (4.3) until it turns purple. This is the end point. Record the volume consumed. Note: hydrochloric acid standard titration solution (4.2) can be used to titrate the distillate of samples with high ammonium content. 7.4 Blank test
Perform a blank test according to the steps described in (7.3), replacing the sample with 250mL of water (4.1). 8.1 The content of ammonium (in terms of N) in the sample, expressed in mg/L, X, is calculated according to formula (1): X
Wherein: Vo is the volume of the sample, mL; bzxZ.net
(V,-v)cx0.01401
V. The volume of the standard hydrochloric acid titration solution consumed at the stoichiometric point, mL; V, — The volume of the standard hydrochloric acid titration solution consumed in the blank test, mL; — The concentration of the standard hydrochloric acid titration solution, mol/L; : 0.01401-
and 1.00mL of the standard hydrochloric acid titration solution [c(HC1)=1.000mol/L L)) is equivalent to the mass of ammonium (in N) expressed in grams,
allowable difference
HG/T2158--91
The ammonium content X in water has a logarithmic relationship with repeatability: 1gr=0.93+0.60 1gX,
The ammonium content X in water has a linear relationship with reproducibility R: R=0.53+0.023 X
HG/T215891
Appendix A
Conversion table of ammonium fluoride concentration
(Supplement)
The determination results of nitrogen mass concentration (NH) or ammonium ion concentration c(NHh) can be expressed by nitrogen mass concentration p(N), (umol/L). The following table lists the conversion factors between them: Nitrogen mass concentration
P(N)mg/L
p(N)1mg/L
p(NH)-1mg/L
umol/L
Ammonia mass concentration
P(NH),mg/L
Example: 1mg/L ammonium ion concentration is equivalent to 0.777mg/L nitrogen concentration Additional remarks:
This standard is proposed by the Science and Technology Department of 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. This standard was drafted by Nanjing Institute of Chemical Technology. The main drafters of this standard are Shen Hongli, Guan Hui and Ni Meizhen. Ammonium ion mass concentration
P(NH4),mg/L
Ammonium ion micromolar concentration
c(NH4), umol /L
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