The Objectives of Qualitative Analysis1 W . L. WASLEY Washington Uniuersity, S t . Louis, Missouri
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HEN a. course . becomes as firmly established as is qual~tatweanalysis in the chemistry cumculurn, i t is easy to accept i t as essential without thought or question. It would be well to make a critical appraisal of the objectives of this course to see whether the course actually does "put across" effectively the material considered to he most important. Systematic qualitative analysis courses were introduced into the curricula of most universities before the turn of the century, and perhaps the only major advance has been the i5troduction of semimicro technique. With the increasing diversity in the activities of chemists a very small proportion of the chemists are ever called upon to make a systematic qualitative analysis after leaving college. Very few find any practical use for the procedures learned in qualitative analysis, and very few indeed remember more than a fraction of the systematic scheme employed in their college course. Assuming, however, that an unusual fellow remembers enough of his "qualmto perform an analysis or that he keeps his college textbook handy, he can a t best analyze for about 25 common metals out of over 90 elements, and perhaps a few common acid ions. Thus, since few ever perform a complete systematic analysis and since even if called upon to do so their analytical scheme would likely prove inadequate, we cannot defend the course as a practical one. The best argument in favor of the course is tbat it teaches the fundamentals of chemical reactions in solutions. All too frequently the average student loses track of this worthy objective while he mechanically performs tests which he hopes will enable him to discover the ingredients of his "unknown." If we are seeking to teach the fundamentals of reactions in solution, ionization and equilibrium constants, solubility products and the like, laboratory experiments could and should be designed better to illustrate these. To find out what chemists not in the teaching profession thought about qualitative analysis as a course, a brief questionnaire was sent to a number of the chemists in the vicinity of St. Louis. The results in Table 1 show that only 52 per cent of those replying TABLE 1 R s s o ~ r sOF S u s v n ~0s CHEMISTS'OPINIONSON
Q O U I T A ~
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thought that qualitative analysis should be retained in the curriculum. Approximately 60 per cent had never performed a qualitative analysis outside of college, ,and of this group which had performed an analysis, over 68 per cent had done less than 10analyses. Sixty per cent of those expressing an opinion felt that more emphasis should be placed upon fundamentals and less on the analytical scheme, while 35 per cent thought that a t least some special methods of analysis could be substituted in place of the usual work. If i t is generally agreed that the fundamentals of reactions in solution, ionization and solubility product constants, and the like constitute the most important part of the qualitative analysis course as taught a t present and that the analytical procedures in the laboratory are of secondary importance, does the present type of course attain the desired objectives? Although some qualitative analysis instrnctors who have expressed opinions on the subject felt that their students were aware of the beautiful interplay of solubility products and ionization constants as they precipitated the sulfides of the various metals, I feel that the average student is almost completely unmindful of such concepts as he struggles with unknowns. To summarize, then, a t its best qualitative analysis teaches students the general properties of the commoner metallic elements along with a few fundamentals of chemical reactions in solutions. Its advocates also claim some benefits derived from the experience in the "scientific method of approach." At its worst, i t encourages careless working. The very nature of the analysis of "unknowns" is apt to lay more stress on the detection of a number of ingredients in a mixture cunningly compounded for the purpose than on the understanding of the principles involved. With the introduction of specific organic reagents and refined instrumental methods of analysis the whole framework of the old systematic qualitative analysis is becoming archaic, and its only justification is its value in teaching general principles. The implication is made tbat the usual type of laboratory work fails to attain the most desired objective of the course, and i t is hoped that thought may be stimulated which will result in t h e development of a more useful and more effective course.
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58% of those anawuing had performed no qualitative analysis outside of college 68% of those who had done any analyses had donelens than 10 62% of those anraving thought qualitative analysis ahodd be retained in cmicvlvrn 60% of thole upraring an opinion rugguted more emphasis on fund*. menfals a5% or thore cx~ressingsn opinionrvggested some norkinspecial methods
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1 Presented before the Division of Chemical Education at the 109th meeting of the American Chemical Society in Atlantic City. A~ril8-12. 1946.
Q ~ ~ S T I O N N SENT A I F ~TO 135 CHEMISTSIN THE ST.LOUIS AREA Outside of college courses. I have performed a b o u t ( 1 , 10, ?) complete systematic qualitative analyses. The usual systematic qualitative analysis course should be re. tained in the collegecurriculum. Y e s No_ UndecidedThe time consumed in qualitative analysis could be utilized t o better advantage in ( ) more emphasis on fundamentals of chemistry ( ) workin special methods of analysis ( ) other suggestions
