For the Zn II -PDMA system, the logK value is 11.48±0.03 and the dominant species is [Zn(PDMA)] -in the pH range between 6 and 9. The [Zn(PDMA)] -complex formation starts around pH 4 and it is highly favorable at pH 6. [Zn(PDMA)(OH)] 2-is present in significant abundance (above 50%) at pH > 9, with logK value of -9.69±0.03. PDMA forms stable complex with Zn II through a wide pH range.