Semimicro Qualitative Analysis

Abstract

The purpose in presenting this discussion of semimicro qualitative analysis is threefold. First, a review of some of the experiences gained in using this method for the past three years at Ottawa University will be presented. Second, the results of a brief survey of the extent to which the semimicro method of qualitative analysis is being used in Kansas colleges and universites are to be given. And third, it is hoped that the presentation of this topic will result in a discussion and exchange of ideas among those interested in this method of analysis. That there is considerable interest in this modification of qualitative analysis is indicated, perhaps, by the response to the survey which was made. Nineteen of the twenty-one schools to which inquiries were directed responded to the survey. A comparison of the macro and semimicro methods of qualitative analysis has been given elsewhere (J. Chem. Educ., 9, 1636 [19321). It is sufficient to state here that the following are some of the advantages claimed for the semimicro method. It is less expensive, it requires greater care on the part of the student, it is more rapid, and unpleasant odors can be kept to a minimum impossible with the macro method. The semimicro method of qualitative analysis has been used at Ottawa University since 1937 in a four-semester hour course for second-year chemistry students. The first two years Engelder, Dunkelberger, and Schiller's textbook,1 Semimicro Qualitative Analysis was used. During the present school year the book, Semimicro Qualitative Analysis by Meldrum, Flosdorf, and Daggett2 was employed. A fairly accurate record of the cost of the semimicro course has been kept. In making purchases, equipment for twenty students was normally secured. For the first two years the cost per student for equipment and supplies not available from the usual chemistry storeroom and required exclusively for introducing the semimicro course was approximately $6.75. Part of the necessary equipment was homemade. Also, the course as originally introduced required a greater number of organic reagents than is used now. Concerning the results of student analyses, Smith3 has reported for a class in semimicro qualitative analysis that in 1,193 times cations were potentially present in the unknown samples issued, in 1,003 times it was correctly reported present or absent, as the case might be. Correct results were therefore reported 84 percent of the time. For the 1939-'40 class at Ottawa University this figure was found to be 89 percent for the cation analysis. It is well to recall in this connection that the unknowns for cation analysis consisted of 2.5 ml. samples, each containing from 3 to 5 mg. of the various individual ions.