[Not Available].
Zinc(II) is titrated with triphenyltetrazolium chloride in the presence of thiocyanate ions. A light yellow, amorphous precipitate of [TT](2)[Zn(CNS)(4)] is formed. Under the same conditions cobalt(II) forms a blue compound, [TT](2)[Co(CNS)(4)], whose solubility product is greater than that of [TT](2)[Zn(CNS)(4)]. This difference between the solubility products allows cobalt(II) to be used as indicator in the titration of zinc(II). Nitrobenzene is employed as a common solvent for the two compounds. At the end-point the nitrobenzene changes colour from light yellow to green.
Alexandrov
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A
Chaire de chimie analytique, Ecole normale supérieure Plovdiv-Bulgarie, France.
Vassiléva-Alexandrova
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