b'ENVIOMETC chelating capacityChelation is a process in which free metal ions combine with ligands to form metalcomplexes. The ability of a chelant to bind metal ion is determined by stability constants.The larger the stability constant, the stronger the chelation effect and the free metal ionin solution become lesser.Table 1: Stability constantsBiodegradable chelants Conventional chelantsEDDS 1 IDHA 3 EDTA 1 DTPA 1 o-o EDDHA 2Ca 2+ 4.6 6.0 10.6 10.7 7.3Cu 2+ 18.4 14.6 18.8 21.5 25.1Fe 3+ 22.0 16.4 25.0 28.6 35.1Mg 2+ 6.0 7.2 8.7 9.3 9.8Mn 2+ 8.6 9.0 13.8 15.6 9.6 4Zn 2+ 13.4 12.0 16.5 18.7IDHA = Imidodisuccinic acid / EDTA = Ethylenediaminetetraacetic acid / DTPA = Diethylenetriaminepentaacetic acido-o EDDHA = o-o ethylenediamine-N,N-bis(2-hydroxyphenylacetic acid)1. A.E. Martell, R.M. Smith, NIST Critically selected stability constants of metal complexes (NIST standard reference database 46, Version 7.0, 2003). LogK values as determined at an ionic strength of 0.1M and at a temperature of 25C or if not available at 20C.2. Isabel S. S. Pinto, et al., Environ Sci Pollut Res (2014) 21:1189311906.3. Miguel A Sierra, et al., Dalton Trans. 2004 Nov 7;(21):3741-7.4. Sandra Lpez-Rayo, et al., Chemical Speciation and Bioavailability (2012), 24(3).ENVIOMETC chelating agents have a low affinity with calcium and magnesium that will result in more stable chelated micronutrient when diluted in hard water and/ or applied to calcareous soils.'