GB/T 15451-1995 Determination of alkalinity in industrial circulating cooling water GB/T15451-1995 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of alkalinity in industrial circulating cooling water
Ind ukstrial circulatt g cooling water--- Determination ofalkalinity
Subject content and scope of application
This standard specifies the method for determining the alkalinity in industrial circulating cooling water. GB/T1545195
This standard is applicable to the determination of alkalinity in industrial circulating cooling water with a content of 2.5 to 1000 mg/L (calculated as CaCO), and is also applicable to the determination of alkalinity in natural water and drinking water.
2 Referenced standards
GB/T601 Preparation of standard solutions for full-scale analysis (volume analysis) of chemical reagents GB/T603 Preparation of preparations and products used in chemical reagent test methods GB/T6682 Specifications and test methods for water used in analytical laboratories 3 Terminology
3.1 Alkalinity
The alkalinity of water refers to the total amount of substances in water that can neutralize strong H+. 3.1.1 Methyl orange alkalinity
By titrating to the endpoint of bromocresol green-methyl red indicator solution, the total alkalinity value in water is randomly determined. It is often used in combination with phenolic acid and alkalinity to determine the concentration of carbonate and bicarbonate or hydroxide and carbonate in water. 3.1.2 Phenolic acid and alkalinity
By titrating to the endpoint of phenolic acid indicator solution, the alkalinity of all hydroxide ions and one-half of carbonate in water is randomly determined. It is often used in combination with methyl alkalinity.
4 Method summary
Using phenolic acid and bromocresol green-methyl red as indicator solutions, the water sample is titrated with hydrochloric acid standard titration solution to measure the phenolic acid and alkalinity and methyl orange alkalinity (also known as total alkalinity).
5 Reagents and materials
In the analytical method, except for special provisions, only analytically pure reagents and those that meet the specifications of grade 3 water in GB/T6682 should be used. The standard solutions, preparations and products required in the analytical methods shall be prepared in accordance with the provisions of GB/T601 and GB/T603 unless otherwise specified.
5.1 Hydrochloric acid (GB/T622); c (HCI) m0.05 mol/L standard titration solution. 5.2 Phenolic acid (GB/T10729); 5 g/1 ethanol solution. 5.3 Bromocresol green (HG/T3-1220) methyl red (HG/T3--958) indicator solution. Approved by the State Administration of Technical Supervision on January 12, 1995 534
1995-10-0/implemented
6 Analysis steps
6.1 Determination of phenolphthalein alkalinity
GB/T15451-95
6.1.1 Transfer 100.00mL of water into a 250mL conical flask and add 4 drops of phenolic acid indicator solution (5.2). If the water sample appears red, titrate with hydrochloric acid standard titration solution (5.1) until the red just fades away. If no red appears after adding phenolic acid indicator solution, it means that the phenolphthalein alkalinity of the water sample is zero.
6.2 Determination of Alkalinity of Methyl Orange
6.2.1 Add 10 drops of bromocresol green-methyl red indicator solution (5.3) to the water sample in 6.1.1 for determination of phenolic acid and alkalinity, and titrate with standard hydrochloric acid solution until the solution changes from green to dark red. Boil for 2Xn, cool and continue titrating until dark red, which is the end point. 7 Expression of analytical results
7.1 The phenolic acidity and alkalinity r of the water sample expressed in mg/L (in terms of CaCO) is calculated according to formula (1): V++c×0.1001
Wherein, Vi-
the volume of the hydrochloric acid standard titration solution consumed when titrating the phenolic acidity and alkalinity, mL; the concentration of the hydrochloric acid standard titration solution, mO1/LV; the volume of the water sample, m
0.1001-the calcium carbonate (CaCO3) equivalent to 1.00mL of the hydrochloric acid standard titration solution (c(HCl)1.000mol/L), expressed in grams O,).
7.2 The alkalinity of methyl orange in water sample expressed in mg/L (calculated as CaCO:) is calculated by formula (2): 0.1001
Where: V—The volume of hydrochloric acid standard titration solution consumed when titrating the alkalinity of methyl orange, mLc—The concentration of hydrochloric acid standard titration solution.mol/L*V—The volume of water sample, mL3bZxz.net
0.1001—The mass of calcium carbonate (CaCO,) expressed in grams equivalent to 1.00mL hydrochloric acid standard titration solution LcHCl) 1.000mol/L3.
8 Allowed integer
Take the arithmetic mean of the parallel determination results as the determination result, and the allowable difference of the parallel determination results shall not exceed 1.5mg/L (calculated as CaCO).
Additional remarks:
GB/T15451--95
This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of Tianjin Research Institute of Chemical Industry, Ministry of Chemical Industry. This standard was drafted by Tianjin Research Institute of Chemical Industry, Ministry of Chemical Industry. The main drafters of this standard are Zhu Chuanjun, Zhou Weisheng, Zhang Yanju, Hong Qian, and this standard refers to the American Society for Testing and Materials standard ASTMD1067--82 "Standard Test Method for Acidity or Alkalinity in Water". From the date of implementation of this standard, the former Ministry of Chemical Industry standard HG5-1502-85 "Method for Determination of Alkalinity in Industrial Circulating Cooling Water" shall be used as the standard.
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