A metal ion indicator dye is used in complexometric titrimetry to determine the changes of complex ion solution produced. Figure 1 shows the minimum pH for effective titration of various metal ions with EDTA. 22 20F Cr 18 Pb Zn Cd + ?? LOG KMY Fe 14 Mn 12 ?? IOF Mg 8 1 1 0 2 4 co 8 10 12 14 pH Figure 1: Minimum pH for effective titration of various metal ions with EDTA (Reilley & Schmid, 1958) i. Describe the effect of pH in the complexometric titration. (4 Marks) ji. Explain the reason of adding small amount of magnesium salt to the EDTA solution used for the titration of calcium with an Eriochrome Black T indicator.