Abstract
(1) The determination of potassium in fertilizers with dipicrylamine reagent using the micro-analytical apparatus with the asbestos filter stick is more simple manipulation of sumple and more rapid than the Chloroplatinate method and the perchlorate method. Also from that this view-point of the accuracy it is found that this method is by no means inferior to the standard method, because the difference between this method and the standard method is less than 1%. This method has, also, the advantage that it requires small quantities of reagent, especially no alcohol, as it is unnecessary to separate from sodium. (2) Sato method using the 0.1N Na-dipicrylaminate (or Ca-dip.) sulution is possible to proceed at room temperature, but it is inferior to the standard method from the view-point of accuracy. (3) The points that we must be careful in this microanalytical method are as follows. (i) The reagent must be dropped, stirring the solution constantly and mixed well with the solution, and the solution must be stirred sometimes after standing in the ice box. (ii) The solution must de kept 0℃ completely. For this reason the freezing mixture is mixed in the ice, but be careful never to freeze in the beaker. (iii) To be careful to wash rapidly with the small qualities of the washing solution onthe account of the solubility of the precipitate.
