| With the wide use of chlorine and formaldehyde in industry and agriculture, people pay great attention to their poisonous effect on the environment. Therefore, it is comparatively more important to analyze and monitor them. Spectrophotometry is by far the most active and available method. For example, the methyl orange colorimetry, which is superior at stableness of color, wide linear range, good precision, accuracy and less disturbance of commonly co-existing ions, has been recommended by the environmental protection councial of China to monitor chlorine concentration in atmosphere. However, the method, which based on the absorbance difference between blank solution and the chlorine-adsorbed solution, is bad in difficult in store and use of reagent, complicated in manipulation and notable influence of temperature and acidity. Furthermore, it's hardly to realize the automatic measurement by this method. Therefore, to develop a new. quick and automatic method becomes a very meaningful job.Based on the fact that the chlorine can fade the acid potassium bromide-methyl orange solution, and formaldehyde can accelerate the rate of potassium bromate oxidating methyl orange, new methods to measure the content of chlorine and formaldehyde with a kinetic mechnism were put forward and detailed theoretics analysis was given in the present work. The theory was proved by a simple set of self-made equipment. The linear range and the RSD for chlorine determination are 2.64ug/L~15.30ug/L, 0.85%~4.63%, respectively, and the linear range and the RSD for formaldehyde determination are 0.091 ~ 1.453ug/mL and 4.80% ~ 8.84%, respectively. Besides maintaining the advantages of methyl orange colorimetry, the present method also reduces the measuring time, realizes the automatic continual measurement, and makes the store and use of the solution more convenient. The method is promising in outdoors analysis of chlorine and formaldehyde because of its convenience and efficiency.
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