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A two-point probe can give undergraduate organic chemistry students experience with measuring polymer conductivity. Polymer conductivity is becoming important but many students still associate electrical conductivity mainly with metals. Students can prepare and dope polymers then use the inexpensive, easy-to-build conductivity probe. The probe uses two copper rods for electrodes. Construction and usage directions are included.

A cost-effective hand-held conductvity meter and probe for small volumes and field work have been developed for general chemistry for nonmajors. The device, with only a ten-step output, gives only a semiquantitative measurement. It is more than adequate, however, for students, enabling them to see the substantial differences in the samples. Output of a battery-driven ac oscillator is sent through a sample with a probe of two graphite mechanical pencil leads embedded in plastic. The current reaches ground through a resister. Students study effects of acid mine drainage on environmental water quality. Students test for iron and sulfate and determine water hardness, conductivity and pH.

The Journal of Chemical Education has published a number of designs of apparatus for testing the electrical conductivity of liquids. The basic design is made up of 2 exposed wires that complete a circuit when dipped into a liquid or touched to a metal surface. A light bulb is used as an indicator of conductivity. An improvement over this design can be built for between $15 and $70.

A low-cost and easy-to-build conductivity meter can be used for qualitative and semi-quantitative conductivity experiments in introductory chemistry courses. Its results are comparable to commercial instruments while it is stable and strong enough to be handled by students. The meter cannot be used for strong acid or very oxidant media because of the limitations of stainless steel electrodes. The multimeter costs about $30 but it can be used with other apparatus and the components for apparatus cost about $20. Construction directions are included.

An audio conductivity device can make the measurement of electrical resistance more interesting to chemistry students because it shows the different resistances by changing the frequency of its audible tones. The device is more sensitive to current flow than most conductivity devices and is inexpensive and easy-to-build. Construction directions and some suggested experiments are included.

An improved version of the quantitative conductance apparatus proposed by D.A. Katz and C.J. Willis is a little more difficult to build but has reproducible quantitative features. The basic elements included in the apparatus are a light-emitting diode, an integrated circuit, an IC PC board, a capacitor, resistors and battery snap connectors. The circuit measures cell resistance. Cell conductance can be determined with the aid of a commercial conductivity meter. Construction directions, a parts list and a circuit schematic are included.

The accuracy and precision of the inexpensive, simply built conductivity apparatus presented by T. Rettich and R. Battino in the Journal of Chemical Education volume 66 on page 168 can be substantially improved with a circuit. The proposed electronic circuit would increase the frequency to 1,250 Hz and would make the voltage stable during measurement. A diagram of the circuit is included as are two experiments that use the conductivity apparatus.