Abstract
Formation constants for the 1:1 and 2:1 complexes formed between Ca2+ and difluoromethylenedlphosphonate (F2MDP), dichloromethylenediphosphonate (Cl2MDP), and 1-hydroxy-ethane-1,1-diphosphonate (EHDP) were determined by a Potentiometrie titration procedure where the Indicator electrode Is a Ca Ion selective electrode and the titrant is a CaCl2 solution. Measurements were made in the absence of Ionic strength control and in 0.10 M NaCl and 0.10 M NH4Cl solution. Logarithm formation constants, although similar for the 1:1 complex, change In the order EHDP > Cl2MDP > F2MDP which is opposite to the acid strength exhibited by the ligands. For the 2:1 Ca2+:llgand complex the EHDP complex formation constant is similar to the 1:1 complex and the complex is significantly more stable than either of the 2:1 Ca2+:Cl2MDP or Ca2+:F2MDP complexes. This Is probably the result of coordination Involving the hydroxyl group In EHDP. Weak 1:1 Na+:ligand complexes were also detected.
Original language | English (US) |
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Pages (from-to) | 1089-1094 |
Number of pages | 6 |
Journal | Analytical chemistry |
Volume | 55 |
Issue number | 7 |
DOIs | |
State | Published - Jun 1983 |
ASJC Scopus subject areas
- Analytical Chemistry