Preparation before calibration

Before calibrating the calorimeter, it is necessary to ensure that the instrument is in a stable state. Place the calorimeter on a horizontal, vibration-free table to avoid external interference affecting the measurement accuracy. At the same time, check whether the components of the instrument are firmly connected and whether the power circuit is normal to ensure the safe and stable operation of the instrument. Prepare standard materials, such as benzoic acid, whose calorific value is accurate and stable, which is an ideal choice for calibrating the calorimeter. In addition, it is also necessary to equip auxiliary tools such as thermometers and ignition wires with suitable accuracy to fully prepare for subsequent calibration work.

II. Instrument cleaning and inspection

Thoroughly clean the oxygen bomb, inner cylinder, outer cylinder and other key components of the calorimeter. Wipe with a clean soft cloth to remove residual samples, dust and other impurities to prevent them from affecting the measurement results. Carefully check the tightness of the oxygen bomb, and observe whether there are bubbles popping up by soaking in water after oxygenation. If there are bubbles, the sealing ring needs to be replaced in time to ensure that the oxygen bomb will not leak during the experiment. At the same time, check whether the agitator runs smoothly and the temperature sensor is sensitive to ensure that all functions of the instrument are normal.

III. Reference material weighing and installation

Use a high-precision balance to accurately weigh the quality of standard materials, such as benzoic acid, and record to four decimal places to ensure weighing accuracy. Put the weighed standard material into the oxygen bomb, install the ignition wire, and ensure that the ignition wire is in full contact with the standard material. At the same time, pay attention not to contact the ignition wire with the oxygen bomb wall, so as not to affect the ignition effect. Fill the oxygen bomb with an appropriate amount of oxygen, and the general pressure is controlled between 2.8 and 3.0MPa to ensure that the sample can be fully burned in a sufficient oxygen environment.

IV. Calibration experiment operation

Put the oxygen bomb with the standard material installed into the inner cylinder of the calorimeter, and connect the ignition circuit and temperature sensor. Start the calorimeter and conduct the experiment according to the operating procedures of the instrument. During the experiment, pay close attention to the temperature change and record the initial temperature, maximum temperature and other key data. After the experiment, calculate the heat capacity of the calorimeter according to the known calorific value of the standard material and the temperature change measured in the experiment. If there is a deviation between the heat capacity and the nominal value of the instrument, the instrument needs to be adjusted accordingly according to the deviation.

V. Data recording and verification

Record all the data in the calibration process in detail, including the quality of the reference material, temperature change, heat capacity calculation results, etc. After completing a correction, repeat the experiment for 2-3 times to verify the stability and accuracy of the correction results. If the deviation of multiple experiments is small, the correction is successful; if the deviation is large, re-check the correction steps to find the problem, and correct again until the measurement accuracy of the calorimeter meets the requirements.

Six, instrument maintenance after calibration

After the calibration is completed, the calorimeter is fully cleaned to remove the residual substances of the experiment. Perform necessary maintenance on the instrument, such as adding lubricating oil to the bearing of the agitator, checking the sealing ring and electrodes of the oxygen bomb and other components to ensure that the instrument is in good condition. Regularly review and calibrate the calorimeter to ensure that the instrument always maintains accurate measurement performance and provides reliable data support for the experiment.