An Inexpensive Electrode Switch The use of ion selective electrodes in research and teaching lahoraTO M i T i R tories ( 1 - 4 ) often necessitates the simultaneous monitoring of two or more ------vCHASSE WOUND lNPUT electrodes with a single millivolt meter and an electrode switch. This is - - - - - - - TO METER ----particularly true in metal complexation studies where hydrogen and metal ion concentrations are monitored. While commercial electrodes switchesareexpensive, ounevperienee has been that reliable switches can L--_---l he constructed easily and inexpensively from readily available materials. While many configurations are possible the one we have found most useful has two electrodes with a common reference electrode as shown schematically. Although construction layout is not critical, care must he taken to prevent floating field effects and eround laoos bv keeoine the outer conductors of the shielded cables connected and bv connectine the switch chassis and &hle shields oniv, at t i e millivolt meter mound. We have found this switehine arraneemeni to orovide &oroducible i ~ n dwi.r-free rcad.ny
