1. Name: solidification point
2. Summary of the method: Put the sample in a prescribed test tube and cool it to the expected temperature. Tilt the test tube to 45° from the horizontal and let it stand for 1 minute. Observe whether the liquid level moves. Use the highest temperature when the liquid level does not move. As the freezing point of the sample, it is expressed in °C.
3. Operation method
①Pour the sample into the dry and clean test tube to the ring mark, and fix the thermometer in the center of the test tube with a stopper, so that the bottom of the thermometer bubble is 8 mm to 10 mm from the bottom of the test tube. Then inject 1 mL to 2 mL of absolute ethanol into the bottom of the sleeve.
Then put the test tube into the sleeve to form the test tube assembly.
② Immerse the test tube assembly in the prepared cooling bath. The temperature of the cooling bath should be 7 ℃ ~ 8 ℃ lower than the expected freezing point of the sample.
③When the temperature of the sample cools to the expected freezing point, tilt the sleeve and test tube assembly immersed in the cooling bath to 45° from the horizontal and keep it for 1 minute. At this time, the sample is required to be still immersed in it. Inside the coolant.
④Then carefully remove the test tube assembly from the cooling bath, quickly wipe the outer wall of the sleeve with absolute ethanol, place it vertically, and observe through the sleeve whether the liquid level in the test tube shows signs of movement, until it is determined that a certain test temperature can make the sample When the liquid surface stops moving and rises by 2 ℃ and the sample liquid surface can move again, the temperature at which the sample liquid surface does not move is taken as the freezing point of the sample.