Determination of freezing point of fatty acid
1. Scope of application: it is suitable for the preparation of water-insoluble fatty acids of oil and the determination of curing temperature.
Definition 2.
Freezing point of fatty acid: Keep stirring liquid fatty acid, and observe the temperature change when the temperature decreases.
When the temperature is blocked, or the temperature rises, the highest temperature is reached, that is, the freezing point of fatty acids.
Principle 3.
Test samples were saponified in a solution of potassium hydroxide in glycerol, soap dissolved in water, neutralized, separated insoluble fatty acids washed with a hot sodium chloride solution, dried and filtered. The fatty acids prepared by melting were continuously stirred to cool down and the curing temperature was observed. The curing temperature was sometimes blocked by temperature drop, and sometimes there was a temporary temperature rise.
4, instrument
4.1: ONE ST-016 automatic fatty acid freezing point tester
5. Determination of freezing point
5.1 Heat the fatty acid to about 10℃ above the predicted freezing point. Pour the fatty acid into the test tube to a height of 55mm, install the cooling device, the thermometer is in the center of the fatty acid, the bottom of the thermometer about 10mm from the bottom of the test tube. Place the jar in a water bath, so that the water level of the bath should be 1cm above the sample level, and agitate it up and down 80-100 times per minute.
5.2 Observe the temperature change, cool down rapidly at the beginning, when the crystal begins to form, the temperature begins to slow down, until the temperature remains constant for 30 seconds or begins to heat up within 30 seconds, stop stirring.
5.3 Record the highest temperature when the temperature is constant or the temperature is rising, that is, the freezing point. Accurate to 0.1 ℃.
6, allow difference
6.1 The allowable difference of the double test results shall not exceed 0.2℃, and its average value shall be taken as the measurement result, accurate to 0.1℃.