Study On The Hardess Testing Method Of Industrial Circulating Cooling Water

Water hardness is one of the important indicator of cooling water,and it can cause the crytallizative scale which is one important part of the dirt of the industrial cooling water system.For this sake,developed a simple,sensitive and accurate method and automatic system for determination,which can be used for the hardness determination of industrial circulating water and natural water.The study is on the basis of Eriochrome Black T(EBT)as indicator and EDTA standard solution as titration in the ammonium chloride buffer solution(pH = 10).When at the end,the solution color changes from red into blue.With the determination of A in the 620 nm,finding the existence of shock absorption,used second-order derivation to determin the end.At the end,it calculates the total quantity of Ca2+ and Mg2+ according to the requirements of EDTA,which is the total water hardness.The results show that this method is simple,sensitive and accurate,and R.S.D<1%,the standard addition recovery is 96.4?103.6%,which can be used for the hardness determination of industrial circulating water and natural water.This paper developed a system of the automatic determination of hardness,which uses the AT89C52 as the core of hardware.It combines the method of Complexometric Titration-Spectrophotometry with the controlling system of Single-chip Microcomputer,achieving the purpose of automatic determination of hardness.At the same time,with the use of the function of single-chip timing and I/O port switch of Single-chip Microcomputer,the system achieves some operations,such as controlling the key of the analysis,on-line analysis,sending the data,cleaning and so on.