The tribasic form is much more soluble than the acid form. Ethylenediaminetetraacetic trisodium salt can be ordered from Aldrich Chemical Co., P.O. Box 2060, Milwaukee, Wisconsin 53201. The disodium form of EDTA is used to treat lead poisoning. The class average data should be used to verify individual results. This investigation may work better after students have developed skills in other simple labs.
Advanced classes can use statistical techniques to examine the significance of their results.
Any medium or large test tube set will work. Tall, small-diameter tubes seem best. Calibrated transfer pipets are available from many sources. Teachers should verify their own results prior to the use of these lesson plans in a classroom setting. Safety glasses or goggles should be worn at all times.