r
To pH 1 mV meter
Low-Cost Reference Electrode for Potentiotitrimetry
I
Patentionetry is a well-established and simple electroanalytical technique that is included in virtually every undergraduate teaching program. I t requires only a suitable potentiometer1pWmV meter, a suitable indicator electrode and a reference electrade. Fabrication of a few inexpensive Wax seal (but not to simple) reference electrodes has been reported in this Journal (I,.?). This note describes yet another method of constructing a simple and low-cost reference electrode. This electrode is most suitable for practical use in teaching laboratories where a large number of electrodes may be required a t once. A 15-cm length of soft-drink straw is taken and 0.5-1 mL of hot Agar solution (1%)saturated Son-drink with sodium nitrate is drawn in and allowed to cool so that about a l-cm long Agar plug is formed Straw at one end ofthe tube. Then, 1-2 m capper sulfate solution (0.010 4 . 1 0 M) is placed over the Agar plug. A 30-cm length of thin copper wire is inserted into the copper sulfate solution. Awax seal is applied to a t the other end of the tube. The other end of copper wire is connected to the pWmV Cu wire meter (see figure). This Cu2+ICuhalf-cell can serves a s a simple, truly low-cast reference electrode in all types of potentiatitrimetry. The potential of this electrode may be simply calculated by using the Nernst equation, or experimentally evaluated by a method reported in reference 2.
Literature Cited
cuso, Solution
Agar plug
1. Randle, T H;Kelly,' J. J. Cham Edm. 11984,61.721. 2. Kctotis, L; Ortega, M. G;Bane., J. A J Cham. Educ. 1980,67,179.
P. Riyazuddin Department of Analytical Chemistry University of Madras Guindy Campus, Madras. 600 025 (India)
Volume 71
Number 2
February 1994
167
