抄録
Colorimetric determination of Potassium with Na-Dipicrycaminate was performed by using the stufenphotometer. The principle of this determination is identical to Amdur's method. But the stufenphotomter was used in the place of electrophotometer. Therefore, the most convienent, condition for Stufenphotometry was investigated. The result was as follows (see fig 1. 2. 3.) ○The filter : - S 47 ○Thickness of solution : - about 20 mm ○Concentration of reagent : - O.3〜0.8% solution of Na-dipicrylaminate was suitable for the determination of 0.1〜0.9 mg K. ○Concentraton of solution for colorimetry : - 0.3cc of supernatant liquid of excess Na-dipicrylaminate soln/100cc of dislilled Water. The effects of foreign ions on this method were discribed below. Na, Ca, Mg does not interfere the determination of potassium with the exception of large amounts of them. Using 0.5mg K the author determind the potassium with accuracy of ±2.5% in the presence of 10mg Na, Ca, Mg (see Table 1 and 2) By this method the determinations of potassium in the plant tissues were made, and their errors were also within ±2.0% (see Table 3). This method can be applicable for the Duboscq colorimeter. The stufenphotometer reading (I/I_0×100) is substituted with the reading of Duboscq colorimeters scale which indicate the depth of 0.02% potassium bichromate solution when both halves of the field appear equally bright. The depth of Na-dipicrylaminate solution for making standard curve is fixed about 1.0〜1.5cm. S. 47 filter is more convenient for this colorimetry. The data were described in table 4 and fig. 4.
