Abstract
In order to determine the constituents on the title, the method, modified ftom that of Spruway's idea (designated as modi.S.method) was studied with some soils. Of phosphoric acid the determination was made by the comparison of blue colour, caused by the addition of ammonium molybdate solution to the soil extract and next of tin Plate of potassium, by the comparison of yellewish brown turbidity of potassium-salt precipitates by the addition of sedium cobalt nitrite soiution to the soil extract and next of ethyl alcohol, Of phosphoric acid the following conclusion was got, namely, the amount, obtained by this modi.S.method.has an inclination of increasing with the increase of so-called available amourt of the acid, determined indirectly by ten years or more continued pot experiment (of rice plant) or directly by electrodialysis.(see Table 3.) Of potassium, to our regret, no concrete conclusion in relation to the available amount, was not get by us.(see Table 3.) Excluding the above relation to the amount, available to the plant, the modified method of this report may be accepted as the rapid method of determinining the cited constituents to such an extent as in about nine gardes for P_2O_5 (see Table 4.)and also in about eight grades for K_2O (see Teble 4)
