GB/T 9104.5-1988 Test method for industrial stearic acid Determination of freezing point GB/T9104.5-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test methods for industrial stearic acids-Determination of titer
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This standard specifies the method for determining the freezing point of industrial stearic acid. UDC 668.1.012
：543.06
GB9104.5—88
This standard applies to the determination of the freezing point of industrial stearic acid produced by hydrolysis of animal and vegetable fats by compression or distillation. 2 Definition
Freezing point: The highest temperature reached when stearic acid solidifies after being cooled to below the melting point according to the prescribed procedure. 3 Instruments
See Figure 1
1-Thermometer, 2-Precision thermometer, 3-Agitator: 4, 5.9--Cork (pad); 6-Water bath; 7-Coagulation tube; 8-Wide-mouth bottle; 10-Weight, 11-Beaker Approved by the Ministry of Light Industry of the People's Republic of China on April 30, 1988 and implemented on October 1, 1988
GB9104.5-88
3.1 Thermometer with a graduation of 0.1℃, 50～100℃, needs to be calibrated. 3.2 The diameter of the coagulation tube is about 25mm, the length is 100mm, and there is a scale about 57mm from the bottom. The tube mouth is equipped with a cork. The cork has two holes, the middle hole is inserted with a thermometer, and the other hole is inserted with a glass (or stainless steel) agitator. 3.3 Wide-mouth bottle 450mL, the inner diameter of the bottleneck is about 38mm, and the bottle mouth is equipped with a cork with a hole of 25mm in diameter. 3.4 Stirrer, glass or stainless steel, with the lower end bent into a ring with a diameter of 20 mm and perpendicular to the rod. 4 Test procedure
Melt the sample at about 30°C, so that its temperature should be at least 10°C higher than the freezing point. Place it in the freezing tube to the scale, insert the thermometer and stirrer, and make the mercury ball of the thermometer about 45mm below the scale. Place the freezing tube in a wide-mouth bottle with a cork, as shown in Figure 1. Keep the water bath temperature at about 30°C, use the stirrer on the thermometer to stir at a constant speed with an amplitude of about 40mm up and down (about 80~100 times per minute), and pay attention to the temperature. When the temperature stops falling for 30s, stop stirring immediately and carefully observe the sudden rise in temperature. 5 Processing of results
The highest temperature that rises is the freezing point of the sample. Take the average of the two tests as the final result. The allowable error of the results of two parallel tests is 0.2°C. Additional remarks:
This standard is proposed by the Ministry of Light Industry of the People's Republic of China. This standard is under the technical jurisdiction of the Daily Chemical Industry Research Institute of the Ministry of Light Industry. This standard was drafted by the Daily Chemical Industry Research Institute of the Ministry of Light Industry. This standard is equivalent to the determination of solidification point in Japanese Industrial Standard JIS K3331 "Industrial Stearic Acid Fatty Acid".
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