Abstract
A rapid volumetric method suitable for potassium in common salt has been made with sodium tetraphenyl boron-mercuric chloride and obtained the following results.(1) The precipitation of potassium tetraphenyl boron is completed by standing for 10 minutes after the addition of the reaent more than 1.6 fold of the theoretical ammount of potassium.(2) For the determination of 0.2-5mg of potassium, the maximum deviation is 0.02mg.(3) The interference of Na ion (up to 1g) is prevented by the presence of a little AlCl3. The presence of Mg 20 mg and Ca 10 mg cause not the interference. This method can be summerized as follows: The test common salt solution of 25 ml (within 5 mg of potassium) is acidified with 0.5 ml of 1 per cent acetic acid and added 5 drops of 0.01 N-AlCl3. Five ml of a 2 per cet sodiumtetraphenyl boron solution is added with stirring and allowed to stand about 10 minutes, the precipitate is filtered throuth a glass filter, washed and dissolved with acetone. About 4 ml of saturated mercaric chloride solution, a little alcoholic solution of methyl red and a measured volume of 0.02 N-NaOH is added and the mixture is boiled for a short time. A 20 per cent solution of KI is added dropwise until the HgI2 precipitate is dissolved. The mixture is titrated with 0.02 N-HCl to a strong red color, then boiled to expel CO2 and backtitrated with the NaOH solution.
