This method is applicable to the determination of water content in pesticide emulsions. GB 3776.1-1983 Determination of water content in pesticide emulsions GB3776.1-1983 Standard download decompression password: www.bzxz.net

1 Scope of application
National Standard of the People's Republic of China
Method of moisture determination for pesticide emulsifiers
This method is applicable to the determination of moisture in pesticide emulsifiers. 2 Reagents
UDC66.063.61
GB 3776.1--83
(Confirmed in 1989)
2.1 Anhydrous methanol: Take 5-6 grams of magnesium chips (or magnesium strips) with a smooth surface and 0.5 grams of iodine, put them in a round-bottom flask, add 70-80 milliliters of methanol (GB683-79) (analytical grade), heat and reflux on a water bath until all the magnesium chips are converted into flocculent magnesium methoxide, then add 900 milliliters of methanol, continue to reflux for half an hour, and then conduct fractional distillation to collect the fraction at 64.5-65℃. The instruments used should be dried in advance, and the place connected to the air should be connected to a drying tube filled with calcium chloride or silica gel. 2.2 Anhydrous pyridine: Pyridine (GB689-78) (analytical grade) is passed through a glass tube filled with granular potassium hydroxide (tube length 40-50 meters, diameter 1.5-2.0 cm, potassium hydroxide filling height is about 30 cm) and then distilled to collect the 114-116℃ fraction.
2.3 Iodine: Re-sublimation, and then dried in a sulfuric acid dryer for 24 hours before use. 2.4: Sulfur oxide: The sulfur dioxide produced by adding concentrated sulfuric acid dropwise to a branch flask containing a paste-like aqueous solution of sodium sulfite, or the sulfur oxide gas released from the cylinder is washed and dried by a concentrated sulfuric acid washing bottle and a calcium chloride drying bottle. 3 Instrument device
The instrument device for moisture determination is shown in the figure below.
100 microammeter
Moisture determination device diagramwww.bzxz.net
1-determination bottle; 2-5 ml dynamic burette, 3-1000 desiccant bottle (containing body + desiccant), 1 dozen balloons: 5-stirring heater;
6-Liquid A: 7-Liquid B; 8-wire electrode (connected to the circuit), 9-waste liquid outlet National Bureau of Standards 1983:0615 Issued
1984-06-01 Implementation
4 Determination procedures
4.1 Preparation of Karl Fischer reagent
GB 3776.1-83
4.1.1 Liquid A: 80 g iodine is dissolved in 1000 ml anhydrous methanol. 4.1.2 Liquid B: After 500 ml anhydrous methanol and 500 ml anhydrous pyridine are fully mixed, 106-107 g dry sulfur dioxide is passed in an ice bath. After reaching the weight, take it out and shake it well, let it stand for one day before use. Both liquid A and liquid B should be placed in a sealed brown bottle. 4.2 Determination of the endpoint
When using the end-point method, the solution is titrated from light yellow to amber as the endpoint. When measuring colored substances or the end point does not change significantly, the permanent stop potential endpoint method should be used. This method uses the permanent stop potential endpoint method as the arbitration method. 4.3 Calibration of Chang Er Fischer reagent
4.3.1 Blank determination: Take 5 ml of liquid B in a measuring bottle, and drip into liquid A under stirring until the amber color is the endpoint (or the microammeter pointer stops at a certain position as the endpoint). Write down the number of milliliters of the deacetylating solution used, and the blank should be measured until it is stable (the values ​​are the same for two consecutive times). 4.3.2 Determination of titer: Accurately weigh 0.02~0.03 grams (accurate to 0.0002 grams) of distilled water and drip it into the measuring bottle, and add 5 ml of liquid B. Under stirring, add liquid A until it turns amber (or the microammeter pointer stops at a certain position), record the milliliters of liquid A consumed, and repeat this process several times. Take the average of the four or more values ​​that are close to it, and the difference between the highest and lowest values ​​should not exceed 0.0001 g/ml.
T (g/ml)
Formula t!: T—Titer of Karl Fischer reagent for water, g/ml; V2
Weight of water, g;
—The milliliters of liquid A consumed by the water sample and blank; V,——The milliliters of liquid A consumed by the blank measurement. W
4.4 Determination of water content in the sample
Use a syringe to absorb 1 ml of sample (at the same time, weigh the weight of 1 ml of sample, accurate to 0.001 g), inject it into the measurement bottle, add 5 ml of liquid B, start the stirring heater, and then titrate with liquid A until it turns amber (or the microammeter pointer stops at a certain position). Write down the number of milliliters of nail polish remover used. Before starting to use, a blank measurement must be performed first. The endpoint of the blank measurement should be consistent with the endpoint of the sample. The moisture content (% x) in the sample is calculated according to formula (2): (V2-V,) × T×100
Wherein: V is the number of milliliters of nail polish solution consumed by the sample; V
-the number of milliliters of nail polish solution consumed by the blank;
-the titer of Karl Fischer reagent, g/ml; W-the weight of the sample, g.
Additional notes:
This standard was proposed by the Ministry of Chemical Industry of the People's Republic of China and is under the technical jurisdiction of the Shenyang Chemical Industry Research Institute of the Ministry of Chemical Industry. This standard was drafted by Nanjing Zhongshan Chemical Industry. The main drafters of this standard are Zhang Junzhi and Tao Deming. 610
(2)
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