Preparation of Water Hardness Colorimetric Card with Calcium Ion as Index

Abstract

The aim of this study was to explore the accuracy of chrome-black T as an indicator for determination of calcium ion concentration in water. By comparing the color changes of the solution under different reaction conditions, the optimal reaction conditions were determined as follows: under the condition of pH=9, the volume of chrome black T was 0.1mL and the reaction time was 10s. The final reaction color is made into a colorimetric card for the determination of water hardness, the results show that at a pH value of 9, chromium black T forms a colored complex with calcium ions, which has good stability, sensitivity, and identification. This colorimetric method has demonstrated high precision, reproducibility, and accuracy in actual water sample testing, and is expected to be widely applied in fields such as domestic water detection and other fields.