INTRODUCTORY QUANTITATIVE ANALYSIS PHIGIP W. WEST Coates Chemical Laboratory, Louisiana State University, Baton Rouge, Louisiana
THE INTRODUCTORY course in quantitative analysis at Louisiana State IJniversity is intended to provide a general training in the theoretical principles applying to analytical chemistry, together with a working knowledge of common laboratory techniqnes. All students who require training in quantitative analysis take the same course, regardless of their major fields of interest. For majors in chemistry additional courses are provided in instrumental methods of analysis, spectroscopy, microanalysis, and other advanced techniques. The complete program of training in analytical chemistry, both undergraduate and graduate has been described recently by Choppin, LeRosen, and West.' The present discussion will be restricted to a description of the basic course and a discussion of teaching and evaluation methods. The educational hackgound of the students to he taught must be considered in the design of any course. The general course in quantitative analysis a t LSU has a prerequisite of a thorough course in qualitative analysis. This tends to ribsure nn ildrquate knowltdp of ionic renrtions and the ntincinles rehtinc to chemicd equilibria. As taught in this department qualitative analysis stresses theoretical principles and analytical separations (including chromatographic separations) rather than its use as an investigative tool. Since all students take the same basic course it is advantageous to use such a prerequisite as a means of establishing the level for instruction so that all students, regardless of primary fields of interest, can undertake the study of quantitative analysis without fear or handicap. AIMS AND METHODS
It seems generally agreed that a begi~iningcourse in quantitative analysis must stress the laboratory art. It is our further belief that all students requiring such training must also have an appreciation of the chemistry and principles encountered in their laboratory work. Furthermore, it would seem ridiculous to train a student in the laboratory mechanics and not teach him how to make calculations necessary for the accomplishment of various analyses and for the expressing of analytical results. Some mention of the significance and treatment of data would also seem justified. It is therefore our aim to present a course in which students learn accepted laboratory techniques which are then practiced with reasonable understanding on representative determinations. 1 CHOPPIN, A. R.,A. L. LEROSEN,AND P. R. WEST. Anal. Chem.. 19, 640 (1948).
As implied in the preceding paragraph, the writer has not agreed with the Professional Tradning Committee's recommended minimum standard for quantitative analysis courses. In the past, this committee has recommended t,hat the minimum standard for such courses be the equivalent of eight hours of laboratory per week for a total of thirty weeks and it was clearly indicated that no lectures would be necessary. The most recent recommendations of the committee are that quantitative analysis should comprise, ". . .the equivalent of thirty weeks of instruction with not less than eight hours a week of which two hours will normally be d e voted to the discussion of principles. This course must include some training in qualitative analysis, if this subject is not covered in the course in general chemist.ry, or in a separate required COU~S~.''
Even these latest recommendations are not sufficiently specific in requiring lectures in quantitative analysis. The writer feels that lectures are as essential to analytical chemistry as laboratory is to organic and physical chemistry. The first semester course a t LSU consists of three hours of lecture and six hours of laboratoly per week for an eighteen-week semester. This is followed by a semester of instrumental analysis a t the junior or senior level. LECTURES
Lectures a t the introductory level are logically intended to aid and supplement laboratory work and provide a real understanding of chemical principles encountered in the practice of analytical chemistry. Discussions of details of procedure, the chemistry of pertinent determinations, and the principal sources of errors are considered an integral part of laboratory work. Lectures on the principles and theories associated with analytical chemistry tend to remove the tendency for students to approach chemistry as a series of empirical operations. Equilibria seem always to require and justify review, and thorough consideration of oxidation-reduction necessitates the presentation of a carefully integrated series of lectures on the balancing of redox equations, determination of equivalency of redox agents, and calculations relating to oxidationreduction equilibria. Also, there is no good reason why students should be sheltered from the Nernst Equation until they reach the courses in physical chemistry. Lecture time devoted to chemical calculations can be justified from a number of standpoints. Understanding of chemical calculations provides an appreciation of the basic operations necessary for the obtaining
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of analytical results. Also, there is little point in col- Students analyze standard samples and i t has been lecting data that are not put in suitable form for inter- found that such a system is entirely satisfactory, both pretation. One reason for emphasizing the calculations from the standpoint of efficiency in issuing samples of quantitative analysis which seems to be generally and from the standpoint of student satisfaction with overlooked is the value of providing students with a the grading system inherent in such a procedure. broader knowledge of accepted procedures for analyses Certain changes are being contemplated in regard -few laboratory courses can include more than a dozen to the laboratory teaching. We are in the process of to two dozen determinations. Selected problems can be preparing visual aids (cartoons) for use in teaching used to call to the student's attention methods and laboratory technique^,^,^ and we expect to introduce alternative methods for the determination of substances some microchemical methods in the near future." not adequately considered in laboratory instrnction. For example, it can be pointed out that lead can be EVALUATION OF THE STUDENT determined gravimetrically by precipitation as the The grading system in quantitative analysis is based sulfate from sulfuric acid or alcoholic solution, by pre- on the use of points. Five hundred points can be cipitation as the chromate, or by electrolytic deposition. earned in lecture. Students are held responsible for Actually, there is seldom need for more detailed knowl- daily quizzes and thirty-five questions are given during edge than this, and the problem work, therefore, the semester's work. In addition, twenty questions provides an excellent means of furnishing students with are given on h a 1 examinations making a total of a general background of acceptable methods. fifty-five questions during the semester. The five Of significance in regard to teaching chemical cal- lowest grades are dropped ancl the total score is obculations is the value of using titers in titrimetric an- tained on the basis of assigning ten points per question. alysis. The use of titers fits in so logically with the In the laboratory, there are eleven determinations concepts of weights and weight factors (chemical fac- which are graded on the basis of fifty points per detertors) that the subject of calculations can be put on a mination, the low grade is dropped making a possible self-teaching basis. A book that is written with this total of five hundred points in laboratory. A combined view in mind is available2and a paper discussing these total of nine hundred points or above constitutes an methods is being prepared for presentation elsewhere. "A," eight hundred to eight hundred ninety-nine It should be pointed out, however, that the concepts constitutes a "B" and so forth. The final examination of titers and normalities are not incompatible and the for the course is taken from current A. C. S. cooperative students a t LSU become proficient in the use of both chemistry tests in quantitative analysis. systems. EVALUATION OF INSTRUCTION
LABORATORY
The scope of laboratory instruction a t LSU has been presented elsewhere.' The choice of determinations studied has been carefully made so that representative determinations are included which serve to exemplify various types of operations commonly encountered in analytical practice. Gravimetly and titrimetry have about equal emphasis while colorimetry plays a less pronlinent role. Although instrumental methods are mentioned in lecture no special emphasis is placed on them in laboratory. The only instruments available for class use are balances, various types of calorimeters and electronic pH meters. The mechanics of laboratory instruction seems to be an important phase of successful teaching. In our laboratories, each student is alloted five feet of desk space for his work. Each student is provided with a balance and calibrated set of weights and there is sufficient equipment available in the individual lockers to provide all of the materials normally required during the semester's work. Instruction is provided on an individual basis with not over 24 students assigned to each laboratory instructor. A major faculty member is responsible for the laboratory a t all times, and instructors must be present whenever students are in the laboratory. No time is provided for unscheduled work. WEST, P. W., "Calculations of Quantitative Analysis," Maemillan Co., New York, 1948.
Questionnaires are distributed to members of the classes as a means of obtaining student evaluation of the instruction. These questionnaires go directly to the dean's office, where the results are tabulated and pertinent remarks and suggestions of the students are noted. Over a period of years it has been found that the students are essentially without prejudice when they fill out these questionnaires, and the results obtained have been of great help in improving the quality of instruction. The use of the A. C. 9. cooperative chemistry test is also to be recommended. Although it is difficult to compare the results obtained locally with those obtained in other institutions, it does serve to point out certain weaknesses and strong points in instruction methods and course setups. The author believes i t would be advantageous in the future if comparisons obtained by means of the cooperative tests could he broken down so as to take into consideration not only the number of semesters which the student has studied quantitative analysis but also the size and nature of the classes, together with the fields of interest of the students tested. ?BLISS, H. H., "Unit Operations of Chemical Analysis," Norman, Oklahoma, University Book Exchange, 1947. RIRTX, H. E.,and B. P. BURTI.,J. CAEM.EDUC.,22, 501 (1945). GADDIS,S., AND G. F. BREUKENRIDGE, ibid., 24, 241 (1947).
JOURNAL OF CHEMICAL EDUCATION CONCLUSIONS
The beginning course in quantitative analysis a t LSU contains certain deficiencies. One possible deficiency is the emphasis placed on classical methods of quantitative analysis. The ideal situation would be to provide all students with a thorough knowledge of hotah classical and instrumental methods. Obviously, this is an ahsolute impossibility and it is felt that the prohlem of instruction is best served through emphasis of the classical methods. It is donhtful that we can justify "modernization" further than to include the use of some organic reagents together with instructions on the use of some common instruments such as electronic pH meters, visual colorimeters, and filter photometers. Probably the most serious deficiency of our course is the lack of laboratory time available to the student. The student is under constant supervision and is under continual pressure. This means that the student has neither the opportunity for personal development nor
the time necessary for real enjoyment of laboratory work, which under ideal conditions should serve to give him both knowledge and enthusiasm. In favor of the present course a t LSU is the fact that most students seem to obtain a reasonable knowledge of quantitative methods. It is interesting to note that in the last national A. C. S. test, premedical students at LSU ranked higher than our chemical engineers, although not as high as chemistry majors. This would seem to indicate that it is possible to give a general course for all types of students provided sufficient foundation is given the nonphysical-science majors to enable them to study without handicap. The one semester course on "classical" methods is justified in that it serves a general need. The instrumental analysis course required of juniors and seniors in the College of Chemistry and Physics is helieved to he the logical place for training in recently developed methods of analysis.
