Complexometric titration

General Requirements for a Good Metallochromic

Indicator are the following, except:

• have two distinct colors

• The color reaction of the indicator with the metal should be specific

• The metal- indicator complex should have sufficient stability, but it should be less stable than metal-EDTA complex

• The metal- indicator complex should have sufficient stability, but it should be more stable than metal-EDTA complex

Murexide form satble complex with all the following metals, except:

• Ca+2

• Co+

• Mg+2

• Ni+

the back titration is useful in the following cases, except:

• If the metal ion precipitate at the pH of the titration

• If there is no suitable indicator

• if the sample is soluble in water

• If the reaction between EDTA and the metal ion is too slow

to increase the EDTA selectivity, we can apply the following procedures, except:

• control the pH

• Adjustment of the oxidation state

• Classical separation

• use of different buffer type

Tetradentate Ligand as :

• Diethylene triamine

• Ethylene diamine

• Ethylene diamine tetra acetic acid

• Triethylene tetramine

all the following factors increase the complex stability, except:

• Ionic Size

• Ionic charge

• Electronegativity

• Extent of Chelation