In response to the growing need of attracting undergraduates to careers in science, these authors developed a laboratory -centered approach to the teaching of general chemistry they call Discovery Chemistry.

This article is unique in its use of a simple physical model to help students taking general chemistry gain a more meaningful picture of the process of light absorption. The approach is empirical and free of calculus.

There is widespread interest in find in^ ways to emphasize the process of investigation in the i'trod;cior) chcmi s t~ cumculum. While there is no uueshon thnt students must continue to learn the fundamekd theories of the discipline and acquire skills in solving related problems, there is a growing appreciation for the value of having students create their own knowledge through a discovery based pedagogy. It is argued that by emphasizing investigative activities in introductory courses we more accurately reflect a way of knowing that characterizes our dynamic discipline (1-9).In 1991 we reported in this Journul that we had implemented a general chemistrv curriculum driven bv a series -of process-oriented, laboratory-based discovery exercises (3). We have continued to refine this "Discovery Chemistry" cumculum, drawing guidance from our original premise that chemistry should be learned in much the same way that chemistry is practiced. Students actively participate in the scientific process as they are guided to rediscover many of the fundamental concepts of chemistry. Instruction in the process of chemistry then serves as a means of introducing the content of chemistry. Consequently, the laboratory experience is given a preeminent role; new information is discovered in the laboratory and then used as the basis of further lectures and discussions. The cooperative nature of the scientific enterprise is simulated by relying on division of the labor, pooling of data, and group discussions of laboratory results. In our previous report we described several examples of student exercises that supported the contention that a general chemistry course could be built around student-generated discoveries. We are now in our fourth full year (six to nine sections per year) of teaching general chemistry to majors and non majors with the Discovery format. Eight different faculty have participated. Our 20 General Chemistry Discovery exercises designed to introduce basic concepts have been through a series of iterations and refinements.A variety of models have been or are being developed for inquiry-based courses. Some, like ours, focus on the rediscovery of fundamental principles. Others draw on current applications of chemistry to stimulate student interest. For instance, at the University of Michigan some laboratory assignments are based upon investigations of current problems in chemistry such as the creation of new painkilling drugs (7). Similarly, a t King's College (Ottawa, Canada) students use an open-ended investigative team approach to study projects that "relate to their experiences of chemistry at work, in the world around them, or to specific areas that are of interest to them" (8). While these programs differ from ours in that the questions asked are more applied in nature, they share our emphasis on chemistry as an investigative laboratory science. Regardless of the exact nature of the program, we note that finding the proper balance between a structured laboratory environment and opportunities for student creativity ...

It Is shown that Immobilization of metal chelating photometric reagents can have the effect of Increasing their selectivity. The ligands studied , 3-(2-pyrldyl)-5,6-bls(4-sulfonatophenyl)-1,2,4-trlazlne and 2 ,4-bls(5,6-bls(4-sulfonato-phenyl)-1,2,4-trlazln-3-yl)pyridlne, become selective for Cu+ over Fe2+ upon Immobilization. It Is argued that the selectivity results from the Inability of the 3:1 (llgand-to-metal) Fe2+ complexes to form due to restrictions Imposed by reagentsubstrate interactions. The Cu+ complex Is affected to a lesser extent due to the less demanding 2:1 stoichiometry.

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