This standard specifies the Karl Fischer direct coulometric determination of ammonia water content in liquid anhydrous (liquid ammonia). This method is applicable to products with a water content equal to or greater than 50 mg/kg. GB 8570.5-1988 Determination of water content in liquid anhydrous ammonia Karl Fischer method GB8570.5-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of water content in liquid anhydrous ammonia
Determination of water content-Karl Fiscker method
Lia#eried whydrows nmmonia -etermimationof wet content-Karl Fiscker method UDC 681.518
GB 85T0.5--- 88
This standard is equivalent to the international standard IS07105-85 "Industrial liquid anhydrous ammonia--Determination of water content-Karl Fischer method". This standard specifies the Karl Fischer direct coulometric determination method of water content in liquid anhydrous ammonia (liquid ammonia). This method is applicable to products with a water content equal to or greater than 50/kg. Note: When the water content is greater than 1000mg/kg, it can be estimated according to the residual content measured in GB8570.3, dilute the evaporated residue with an appropriate amount of anhydrous methanol (3.4), and then take a certain amount of the diluted solution for determination. Reference standards
GB8570.1 Collection of laboratory samples of anhydrous ammonia GB8570.3 Determination of residual content of liquid anhydrous ammonia by gravimetric method GB6283 Determination of water content in chemical products by Karl Fischer method (comply with the method) 2 Method
After evaporating the liquid ammonia sample in the presence of ethylene glycol, a quantitative reaction is carried out using water and Karl Fischer reagent (a solution composed of iodine, iodine dioxide, and pyridinium methanol).
H,O+ 12 + SO +3C.HN+ROH 2C.HN.HI+C,H,NH.OSO2OR The water content of the evaporation residue is determined by direct coulometric method. 3 Reagents and solutions
In the analysis, unless otherwise specified, only analytical reagents, distilled water or water of equivalent purity are used. 3.1 Refrigerant: a mixture of solid carbon dioxide (dry ice) and industrial alcohol, with a refrigeration temperature of 35-40°C: 3.2 Sulfuric acid (GB625-mm7): about 10% (m/m) solution 3.3 Ethylene glycol (HGB3318-60): the water content is not more than 0.1% (m/m). If the water content exceeds, add about 50g of 5A molecular sieve to 500ml of glycol, plug the bottle, shake it, leave it overnight, absorb the clear liquid for use, note: ethylene glycol is extremely hygroscopic to prevent the influence of moisture in the atmosphere. 8. Methanol (GB683-79): the water content is not more than 0.03% (m/m). If the water content exceeds, treat it according to the method specified in 3.3. 3.5 Glacial acetic acid (GB 67678): = 1.05g/L, 3.6 Methanol-acetic acid solution: 100ml glacial acetic acid (3.5) and 900ml methanol (3.4) mixed 3.1 Karl Fischer reagent: prepared according to GB6283.12 3.8 Sodium tartrate (HG31101-77) or water * 8.8 Methyl red (HG3--958--76): 1g/L 95% (V/V) ethanol solution 3.105A molecular sieve: 35mm diameter granular desiccant, use Before use, calcine at 500℃ for 2 seconds and then cool in a dryer containing molecular sieve. The used molecular sieve can be reused after washing with water, drying and calcining. 3.11
Active silica gel: used as filling desiccant
Approved by the Ministry of Chemical Industry of the People's Republic of China on December 2, 1987 131
Implementation on September 1, 1988
GB8570.5-88
3.12 Silicone grease: used to lubricate glass pistons and ground joints. 4 Instruments
Usually laboratory instruments and:
4.1 Sample sampling device
Assemble the instrument according to the provisions of Article 4.1 of GB8570.3 and its attached figure. 4.2 Direct coulometric titration device
Assemble the instrument according to the provisions of Article 5.1 of GB6283 and its attached figure. The glass components used should be dried and the ground joints should be lubricated with silicone grease (3.12).
5 SamplingWww.bzxZ.net
Take laboratory samples according to GB8570.1. 6 Operating procedures
6.1 Sample collection
Weigh the mass of two conical flasks A and B, each filled with about 500ml sulfuric acid solution (3.2) and 2 drops of methyl red solution (3.9), and connected with connecting tubes from connection point 5, and weigh to 0.1g. Immerse the test tube without a stopper in the refrigerant (3.1) in the Dewar flask to three-quarters of the depth. Add 2.0ml ethylene glycol (3.3), stopper it, and connect conical flasks A and B.
The following is the operation according to GB8570.3 6.1 starting from "rotate piston 3 to seal the test tube, 1 and 2 ends..." to take the sample.
6.2~Calibration of Karl Fischer reagent
In the titration vessel of the direct coulometric titration apparatus (4.2), add methanol (3.4) until the electrode is submerged, turn on the power supply, turn on the electromagnetic stirrer, adjust the instrument so that the ammeter indicates a low current (usually a few microamperes), and drop Karl Fischer reagent (3.7) to react with the trace amount of water in the methanol until the ammeter pointer suddenly produces a large deflection and remains stable for at least 1 minute. In a small glass tube, weigh about 0.250g of sodium tartrate (3.8), accurate to 0.0001g, remove the penicillin bottle stopper, quickly add it to the titration vessel, and then weigh the small glass tube again to determine the mass of sodium tartrate added by subtracting the difference. You can also add about 0.040g of water from a dropper bottle, weigh the mass of the dropper bottle before and after adding it to the titration vessel, or use a 10-50μ1 micro syringe to inject water into the titration vessel through the penicillin bottle stopper. Titrate the known amount of water added by one of the above methods with the Karl Fischer reagent (3.7) to be calibrated until the pointer of the ammeter reaches the same deflection and remains stable for at least 1 minute. Record the volume of the Karl Fischer reagent used. 6.3 Determination
Take out the test tube containing the sample from the Dewar flask and allow ammonia to evaporate slowly through both ends at room temperature until the bottom of the test tube is an evaporation residue composed of ammonia water, ethylene glycol and other non-volatile substances at room temperature. Drain the residual liquid in the titration container through the drain nozzle, add methanol (3.4) to the titration container until the electrode is submerged, turn on the power supply, turn on the electromagnetic stirrer, and add Karl Fischer reagent (3.7) dropwise as in the calibration process until the pointer of the ammeter reaches the same deflection as the calibration, and remains stable for at least 1 minute.
Open the test tube and add 10.0 ml of methanol-acetic acid solution (3.6) to allow it to flow down the tube wall. After carefully shaking, quickly transfer to the titration container, continue to wash the test tube with 10.0ml methanol-acetic acid solution several times, until the maximum amount is 50.0ml, quickly transfer all the washing liquid to the titration container.
Use the same operation method as the calibration, titrate with Karl Fischer reagent until the ammeter pointer reaches the same deflection and remains stable for at least 1min as the end point, and record the volume of Karl Fischer reagent used for titration. 6.4 Blank test
Carry out a blank test with the same time, operation procedures and the same amount of reagents (except Karl Fischer reagent) used for the determination, without using the sample.
7 Expression of results
GB 8570.5--88
7.1 The water equivalent T of Karl Fischer reagent (3.7), expressed in mg/ml, is calculated according to formula (1) or (2): mz×0.1566
Wherein: m1 is the mass of sodium tartrate added when calibrated with sodium tartrate (3.8), mg3m2 is the mass of water added when calibrated with water, mg, Vl is the volume of Karl Fischer reagent used for calibration, ml, 0.1566 is the mass coefficient of sodium tartrate converted to water. 7.2 The water content X expressed as a mass percentage is calculated according to formula (3): X
Where: mo--
T (V2-V3)
mo×10
（2）
The mass of the sample [the number of milliliters of liquid ammonia collected in the test tube multiplied by 0.68 (0.68g/ml is the density of liquid ammonia) and the sum of the mass increments of the two conical flasks and the attached connecting tubes starting from the connecting point 5], gT——the water equivalent of Karl Fischer reagent calculated according to 7.1, mg/ml, V2——the volume of Karl Fischer reagent used for titration, ml, V——the volume of Karl Fischer reagent used for blank test, ml. 7.3 Allowable error
7.3.1 The arithmetic mean of the results of two parallel determinations is taken as the determination result. 7.8.2 Absolute allowable difference of parallel determination results: moisture, %
Absolute allowable difference, %
Additional remarks:
This standard is under the jurisdiction of Shanghai Research Institute of Chemical Industry, Ministry of Chemical Industry. This standard was drafted by Shanghai Research Institute of Chemical Industry, Ministry of Chemical Industry and Wujing Chemical Plant. The main drafters of this standard are Yin Yongkang, Jin Zhigen, Yao Bingsheng, Liu Miaode and Zhang Wenwei. 136
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