Determination of potassium by an automatic ultraviolet absorptiometric method

An automatic ultraviolet absorptiometric method has been developed for the determination of potassium. The method involves precipitation of potassium by addition of a known excess of sodium tetraphenylborate, removal of the potassium tetraphenylborate precipitate by filtration, and measurement of the excess of sodium tetraphenylborate in the filtrate by means of its absorbance at 254 mμ;. Most of the apparatus, including a continuous filter, is standard AutoAnalyzer equipment but a Uvicord ultraviolet absorptiometer replaces the conventional colorimeter. Build-up of precipitate in the system is eliminated by immersing the mixing coils in an ultrasonic bath which is actuated intermittently by a simple timing mechanism. The method is especially suitable for potassium analysis in production plant where flame photometer results are sometimes affected by fertilizer dust in the air surrounding the burner.