Chlorine gas is a widely used gas in the field of chemical industry. At present, more than 60% of the chemicals in China use it in the manufacturing process. Chlorine gas is a kind of poisonous and harmful gas, which mainly penetrates human body through respiratory tract, so chlorine gas sensor is used to detect the chlorine gas content in the air, so as to achieve the early warning effect of chlorine gas leakage accident. In order to ensure the accuracy of the test results, it is necessary to calibrate the instrument with chlorine gas mixture in nitrogen.

At present, the widely used field gas detection technology mostly USES the catalytic combustion, electrochemistry, semiconductor and photoionization and other small practical gas sensors. In order to ensure the reliability of the measurement results of chlorine gas sensor, the standard substance in nitrogen is prepared by weighting method, which is a basic method recognized by the world.

The mixture of chlorine gas in nitrogen was prepared according to the national standard of weighing method, and its value was determined based on the weighing results. Considering chlorine gas has strong toxicity and reactivity, the dilution step should be minimized to reduce the risk of chlorine gas leakage and reaction. Therefore, we use trace transfer technology to prepare chlorine gas mixture in nitrogen.

Precision electronic comparator is used to accurately weigh the cylinder before and after filling according to the requirement of preparing gas standard material by weighing method. The difference of the result of weighing is the mass of the added gas. The molar fraction and uncertainty of chlorine gas in mixed gas are calculated according to the mass of added gas, the purity of raw gas and the molecular weight of component. The results show that the uncertainty of the weighting method for the chlorine gas mixture in all nitrogen is 0.2%-0.4%.