Here are two mediation methods for Beckmann temperature range:
First, the constant temperature bath mediation method
1. First determine the temperature range used. For example, measuring the decrease in the freezing point of an aqueous solution requires reading a temperature reading between 1 ° C and -5 ° C; measuring the increase in the boiling point of the aqueous solution is expected to read a temperature reading between 99 ° C and 105 ° C; as for the determination of the heat of combustion, The mercury column at room temperature is most preferably between 2 and 3 °C.
2. Depending on the range of use, estimate the temperature at which the mercury column rises to the end of the capillary. In a typical Beckman thermometer, the mercury column rises from the highest point of the scale to the end of the capillary and needs to be raised by about 2 °C. The amount of mercury in the mercury ball is adjusted based on this estimate. For example, when the freezing point of water is lowered, the maximum temperature reading is intended to be adjusted to 1 ° C, then the temperature at the end of the capillary tip should be equivalent to 3 ° C.
4. Using a constant temperature bath, adjust it to the temperature at which the elbow of the capillary end should reach, and place the Beckman thermometer in the constant temperature bath at a constant temperature of 5 °C or higher.
5. Remove the thermometer and hold it in the middle with your right hand so that it is nearly vertical. Use your left hand to gently tap the right arm, as shown in Figure 3-3. At this point the mercury can be broken at the elbow. After the thermometer is taken out of the constant temperature bath, the mercury volume will change rapidly due to the temperature difference. Therefore, this adjustment step requires quick and brisk, but there is no need to panic to avoid mistakes.
6. Place the adjusted thermometer in a constant temperature bath at the predicted temperature, observe the reading value, and estimate whether the range meets the requirements. For example, in Experiment 2, the freezing point of the freezing point method can be tested by using an ice water bath of 0 ° C. If the temperature value falls at 3 to 5 ° C, it means that the range is appropriate. If the deviation is too large, it should be re-adjusted according to the above steps.
Second, the ruler reading method
This method can be used by people who are skilled in operation. The method is to directly use the temperature scale on the upper part of the Beckman thermometer, without having to adjust it with a constant temperature bath. The operation steps are as follows:
1. First estimate the maximum operating temperature value.
2. Invert the thermometer so that the mercury in the mercury ball and the capillary is slowly injected into the ball at the end of the capillary, and then slowly tilt the thermometer to connect the mercury in the tank.
3. If the estimated value is higher than room temperature, use warm water, or an inverted thermometer to use gravity to allow mercury to flow into the mercury storage tank. When the mercury surface at the temperature scale reaches the desired temperature, tap gently as shown in Figure 3-3. The mercury column is disconnected at the elbow; if the estimate is below room temperature, the thermometer can be immersed in a lower constant temperature bath, and the mercury surface is lowered until the reading on the thermometer gauge reaches the estimated temperature. Disconnect the mercury column.
4. Same as above, whether the amount of mercury adjusted by the experiment is appropriate.
Precautions
First, the Beckman thermometer is made of thin glass, which is much longer than the average mercury thermometer and is susceptible to damage. Therefore, it should be placed in the thermometer box, or installed on the instrument rack, or held in the hand. Should not be placed arbitrarily.
Second, when adjusting, be careful not to let it be hot or cold, but also avoid heavy blows.
Third, adjust the thermometer, be careful not to connect the mercury column in the capillary to the mercury in the storage tank.
File Storage Box,Small Storage Bins,Paper Tray Organizer,Computer Desk Organizer
Fuzhou Will Trade Import and Export Co., Ltd. , https://www.will-trade.com