Pedosphere 1(4): 363--369, 1991
ISSN 1002-0160/CN 32-1315/P
©1991 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Direct Determination of Potassium-Sodium Activity Ratio in Soil Suspension with Two Ion-Selective Electrodes |
| LI HONG-YAN, JI GUO-LIANG |
| Institute of Soil Science, Academia Sinica, P O. Box82l, Nanjing 210008 |
| ABSTRACT |
| A K+-selective electrode and a Na+-selective electrode were used to construct a measuring cell without liquid-junction for the determination of the ion activity ratio of K+ to Na+ in soil suspensions. The measured cell potential was not affected by the total electrolyte concentration when the total cation concentration was 10-1 -10-3 mol L-1 and the concentration ratio CK+/CNa+. was 10:1 to 1:50. When the concentration ratios were equal to 1and the total electrolyte concentrations were 10-2 and 10-3 mol L-1, the ion activity ratio measurement would not be affected by pH in the pH range of 3.5 to 11.5 and 4.4 to 11 respectively. Ions other than H+ have no remarkable influence on the measurement. The ion activity ratio of K+ to Na+ measured directly in soil suspension agree well with those in centrifuged supernant solution. The relative deviation was within 4%. From the measured ion activity ratio, the difference of the bonding energies of K+ and Na+ ions was calculated. |
| Key Words: |
| Citation: Li, H. Y. and Ji, G. L. 1991. Direct Determination of Potassium-Sodium Activity Ratio in Soil Suspension with Two Ion-Selective Electrodes. Pedosphere. 1(4): 363-369. |
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