Abstract: In slightly acidic or alkaline solution of acetate, sodium tetraphenyl-borate (Na-TPB) gives a sharp incision on its oscillopolarogram which can be used to indicate the end point of titration Involving Na-TPB. In the determination of K, excess of standard Na-TPB solution is added to precipitate the Kions in alkaline (PH=12) solution and part of the mixture is filtered through dry filter paper and the excess TPBin the filtrate is titrated with T1(I) solution. Divalent and trivalent ions that precipitate in alkaline solution do not interfere with the determination.Pb⁺² and Sn⁺² ions that distort the oscillopolarogram of TPBcan be masked by EDTA. The method is very simple, accurate and rapid. Thin film Hg electrode is used as a polarized electrode, and the Hg-coated Ag electrode as a depolarized electrode.