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6455708 
Journal Article 
The use of the antimony electrode for determining the pH value of soils 
Barnes, EES 
1932 
Yes 
Agronomy Journal
ISSN: 0002-1962
EISSN: 1435-0645 
24 
2 
156-161 
The antimony electrode gave results in good agreement with the colorimetric method and gave constant results over a 5-minute period, while the quinhydrone electrode gave too high results even in the first reading. On a soil obtained from Hawaii, which showed by colorimetric test to have a reaction of 5.5 pH, the same value was obtained with the antimony electrode, while with the quinhydrone electrode the first potential balance that could be obtained indicated a pH of 7.0 and rapidly increased with time. Our experience has been that the antimony electrode does not work well in the presence of large quantities of hydroxy acids, such as citric, tartaric, and malic, and at least some of the amino acids when present in large quantities affect its accuracy. Soils, however, seldom if ever contain these substances in sufficient quantities to affect the accuracy of the determination. It would seem that the antimony electrode furnishes another tool for determining the reaction of various substances including soils. It works well in determining the reaction of milk, urine, agar, and silicic acid gels. The antimony electrodes used in this work (Fig. I) were cast from C. P. antimony by drawing some of the molten metal up into a pyrex glass tube. As soon as the metal had solidified the glass tube was sprinkled with cold water. This caused the glass to break into small pieces and made removal easy. The resulting antimony rod was trimmed up on the ends into the shape of a cylinder and a piece of copper wire was soldered on the end. The wire and the end of the antimony rod were then inserted into a piece of pyrex tubing of the same size as that used for a mold and cemented in with DeKhotinski cement in such a manner that about an inch of the antimony rod projected from the end of the tube and the copper wire extended out through the other end of the glass tube. If the electrode has stood for some time since being used, it is always wise to cheek it against a buffer solution of known pH value before using it. If it does not give the correct potential for the solution, it will likely be too high. The authors have found the following procedure sufficient to adjust the electrode: The antimony which projects from the glass rod is sandpapered with No. 00 sand paper until it is bright. It is then heated gently in the blue flame of an alcohol torch until it is coated with oxide. It should then be checked again in the standard buffer solution and if it is too low in potential it should be heated again. Should too much oxide be formed so that the electrode gives too high a potential, it should be lightly sandpapered. 
; soil pH; laboratory equipment; electrodes; antimony/