イオン交換体による陽イオンの分離（第Ⅶ報） : 土壌および天然水のイオン交換分析

Ion exchange separation using hydrochloric acid and formate buffer solution as eluants wareported in the previous papers. Na, K, Mg, Ca, Mn, Al and Fe are separated from each other satisfactorily. In this paper the authors studied to analyze soils and natural waters in this method. Exchangers used are Dowex 50W-X8 and Diaion SK#1, each being a strong acid resin of polystyrene. The eluants are prepared mixing 1 mol/1 formic acid and 1 mol/1 ammonium formate, thus controlling pH of the solution from 3.2 to 4.0. Fe, Na and K are separated together with pH=3.2, Al with pH=3.4, Mn and Mg with pH=3.4 or pH=3.6, and Ca with pH more than 3.8 respectively. The group of Fe, Na and K is eluted with hydrochl-oric acid on the other column of the same kind of exchanger. Na is separated with 0.2?-HCl, K with 0.5?-HCl, and Fe with a formate buffer solution of pH=3.2 succeedingly. Separation of the group of Mn and Mg is rather difficult, unless a long column of an exchanger is used. Except in the case of including very small quantities of cations, the cation-exchange data showed good accordance with the ordinal method of analysis. Effect of addition of methanol to the eluants was also studied in this paper, resulting in prefarable separation of cations, espec-ially for alkali metals.