3.2. Sample preparation
Samples of the chlorine solution are also needed to test our proposed concept. In this case, we choose to dissolve calcium hypochlorite in water as it is typically used in the chlorination process for drinking water and swimming pools. A 6 ml chlorine solution is brought into a small glass bottle having 1 mm thick, 20 mm outer diameter, and 73 mm high. After that, 80–100 μl of KI–starch solution prepared earlier is dropped into 6 ml of the chlorine solution. Fig. 2 shows chlorine solutions with 13 concentration levels mixed with the KI–starch solution for at least 10 s. It can be clearly observed that there is a color change in only one tone. As the concentration of the chlorine in water gets increased from 0 ppm to 2.0 ppm, the chlorine solution mixed with the KI–starch solution under a white reference background gradually changes its color from white to light blue and stops at dark blue.