Polarography of Potassium Tetraphenyl borate( 111) in N,N '-Dim ethy If o rmamide A R T H U R F. FINDEIS, JR., and T H O M A S D E VRIES D e p a r t m e n t o f Chemistry, Purdue University, Lafayette,
Ind.
A recording polarograph was used to obtain polarograms of potassium tetraphenylborate(II1) dissolved in N,A"-
larography in this lahoratory. I t readilj. dissolves potussiuin tetraphenylborate and is suitable as a solvent for obtaining polarographic waves of the potassium ion. Iiemula and Kornacki (3)have determined potassium in the 0.1- to 1.0-my. range by precipitation with excess sodium tetraphenyltiorate and harktitrating with 0.005X t,hallous nitratr. dctrrmining the r i d point amperometrically.
dimethylformamide with tetrabutylammonium iodide as the supporting electrolyte. The wave heights were proportional to concentration over the range 0.0002 to 0.0075M which corresponds to 0.08 to 3.0 mg. of potassium in the polarograph cell. The half-wave potential was -1.55 volts with a mercury pool as nonpolarizecl electrode.
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APPARATUS AND 3IATERIALS
Apparatus. .411 polarograms were obtained using a Leeds & Xorthrup Electro-Chemograph, Type E. A mercury pool cell was cwnstructed out of an 8-mm. test tube, with a side arm at the bottom to degas the sample. The cell was designed in such a wiy as to contain 10 nil. of solution x h e n about half full and it w:ts immersed in a \\.:iter bath with the temperature controlled at 25" =I= 0.1" c. The capillary used for the dropping mercury electrode TVRS prepared from Corning iniirine imrometer tubing of 28.4-micron radius and IO-cm. length. 7/12 was determined at -2.0 volts, Ivhich correspond. to t h e p h t c a u of the potassium w a w j and found t o have the coIi.qt:iiit v:ilue 1 . 3 i 6 , even though m ant1 f irere not coilstarit. T h r rc11 rwistance was 920 ohms and the dropping mercury elerti,od
