In the work of calorific value detection, the accuracy of the calorimeter directly affects the reliability of the detection results, and the calibration of benzoic acid is the core link to ensure the accuracy of the calorimeter. The following is a detailed introduction to the specific operation process of the calorimeter to calibrate benzoic acid.

preparatory work

First of all, make sure that the calorimeter is in a stable operating state, check whether the components of the instrument are connected normally, and the parameters such as power supply and water temperature meet the requirements. At the same time, prepare benzoic acid with a purity of ≥ 99.9%, grind it into a uniform powder, dry it in an oven at 105 ° C for 1 hour, and cool it to room temperature for later use. It is also necessary to prepare a special tablet press, ignition wire, oxygen bomb, and analytical tools to ensure that all appliances are clean and dry.

Benzoic acid tablet operation

Use an analytical balance to accurately weigh about 1g of benzoic acid powder and record the exact quality. Put the weighed benzoic acid into a tablet press mold, and slowly press it into a dense disc to ensure that the surface of the disc is smooth and free of cracks. After the pressing is completed, gently remove the benzoic acid sheet, fix it on the electrode holder of the oxygen bomb with forceps, and connect the ignition wire. Note that the ignition wire is in good contact with the benzoic acid sheet to avoid loosening.

Sampling and Oxygen Bomb Assembly

Put the inner cylinder of the oxygen bomb equipped with benzoic acid into the outer cylinder of the calorimeter, inject 10ml of distilled water into the oxygen bomb, and tighten the oxygen bomb cover to ensure that there is no leakage in the seal. Fill the oxygen bomb with 3.0MPa of oxygen through the oxygen filling device, let it stand for 15 seconds, and check whether the oxygen bomb is leaking. After confirming that it is correct, put the oxygen bomb into the measurement position of the calorimeter.

Calibration operation and data processing

Start the calorimeter and start the calibration test according to the instrument operation process. After the test, record the temperature rise data displayed by the calorimeter, combine the exact quality and standard calorific value of benzoic acid, and calculate the calorimeter's heat capacity through the formula. Repeat the calibration 3-5 times, and take the average value as the final heat capacity value to ensure the accuracy of the calibration results.

Precautions

During operation, it is necessary to strictly abide by the operating specifications of the instrument to avoid benzoic acid being damp or contaminated with impurities; the pressure during oxygenation should be strictly controlled within the specified range to prevent danger caused by overpressure; the laboratory environment should be kept stable during the calibration process to avoid temperature fluctuations affecting the test results.

Mastering the method of calibrating benzoic acid with a calorimeter can not only ensure the detection accuracy of the instrument, but also provide reliable data support for the calorific value detection work, and help the detection work to be carried out efficiently.