Rubye P. Torrey Tennessee State University at Nashville Nashville. 37203
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Teaching for Learning The modular approach to analytical chemistry laboratory
The modular approach to teaching analytical chemistry laboratory is the result of the author's own personal feeling about instruments. She has long felt that there should be a way to teach students the basic fundamental principles and the use of instruments without investing in costly commercial instruments. This kind of thinking was enhanced by the fact that Tennessee State University is not one of the more affluent schools. The A.R.F. line of instrumental modules came out just in time. Prior to this the author had worked with the Heathkit modules, but felt that they were less well suited for her purpose. The fast pace a t which directions change in chemistry ( I , 2), and the misconception mans scientists-even chemistshave of analytical chemistry, have caused the author to engage in serious reflection and address herself to the question: What is the direction in which the teaching of analytical chemistry should proceed? Stated another way, one mav.ask.. "Whither " eoest thou?" The area of analytical chemistry has undergone many changes in the last few years (3-9). Although i t is extremely vital to any scientific discipline, and particularly chemistry, bioloev. and the allied health sciences. there are those who woula-like to think the analytical course could very easily be left out, or its content divided between general and physical chemistry. This plan could never wogk too satisfactorily becauke analytical chemistry has its own place to fill. - - ~ In no discipline have the changes brought about hy modern technology been more manifest than in analytical chemistry. These multitudinous, rapid changes can easily make the teaching of analytical chemistry a challenge ( I & 1 4 ) . One may ask: How is it possible to equip a student with all the many necessary procedures and techniques required to cope with the outside technical world by exposure to one or two courses in analytical chemistry in college? The answer, of course, is very clear-Teach the Basic Fundamentals. Too often analytical chemistry is taught as if it were an abbreviated orientation course for technicians. in that the students are instructed t o "flip" switches and he "blackbox" operators instead of students of chemistry. Here a t Tennessee State University, an attempt has been made to teach analytical chemistry laboratory in a manner that will give the student the kind of knowledge that is transferable. In order to put this method of approach in proper perspective, let us reflect for a moment. Approximately 30 years ago, the college course in analytical chemistry was called Quantitative Chemical Analysis, and was offered in the sophomore year. Around the late 40's and early 50's a period of expansion of undergraduate schools started, and many schools added a second analytical course a t the senior level. which was called Instrumental Methods of Analysis. In &any instances this became the "switch-flipping" course. Students ran through numerous experiments using rather expensive commercial instrumentation in "cookbook" fashion. Prior to class time, the teaching assistant or professor would check out the performance of the instrument and determine all the instrument settings. Students would come into class with their samples, analyze them in assembly-line fashion and fill in the blanks on a data sheet that was provided in mimeographed form,
or in their Manual. This kind of experience is better than no experience; however, i t leaves much to he desired in the realm of transferable knowledge. The analytical course at Tennessee State University is a combined lecture-laboratory, junior-senior level course carrying five semester hours of credit. The lecture and laboratory may be taken separately with the lecture carrying three hours credit and the laboratory two hours.' Formal lectures are presented twice a week with the third weekly session being devoted to either a "talk" session or a test. The number of students enrolled in the course has ranged from six to twenty. They are either professional chemistry majors, premedical science students with a concentration in chemistry, or are pursuing an allied health profession curriculum. In general, the students will have had two to three years of chemistry, one year of college physics, and one to two years of college mathematics. This course. which is called Analvtical Chemistrv. is somewhat a merger of the traditional ~ u a n t i t a t i v e~ n a i i s i s and Instrumental Analysis courses with updating and revision. In the past, a traditional quantitative analysis course a t the sophomore level and an instrumental course a t the senior level were taught. The sophomore course was a yearlong course and the instrumental course lasted for two quarters. Now, Analytical Chemistry runs for a full year and replaces the other two courses. A text is not used in this c o u r ~ ethe , ~ purpose of which is to give the students experience in reading several author's viewpoints, synthesizing their own definitions and descriptions, and finally drawing their own conclusions. The students are given a reading list with comments and addresses. They may purchase any or all of these books if they desire. At least two of the books on the list will be found in the University Book Store, and several will he found in the University Library. The lectures are more or less conventional, aided by the use of many demonstrations and other visual aids. The laboratory activities are initiated with a slide-tape presentation accompanied by a script and followed by performance of the activity. The script gives general directions for performing the experiments, precautions, and items to he included in the written report. The script is generally distributed one week before the experiment is to be performed. The slide-tape presentation is given a t the beginning of the laboratory period in which the activity begins. Writing the scripts for the activities or experiments is the result of the author not finding a book exactly suitable. Most texts annear .. to be written for either the short introductory course, or a fairly sophisticated senior-level course. The slides were added as a means of involvine the students. They were asked to help in preparing someuof the experimental arrangements used on the slides. In a few instances The semester system is now in effect at our school. Prior t o this year we were on a quarter system. The course carried four credit hours each quarter, and could not he registered for separately. Students are still eneouraaed to take the lecture and laboratory simultaneously. Not using a text does not mean not buying a hook. It simply means that the students may choose the books they purchase from a list of several suggested on a reading list. Volume 53,Number 1. January 1976 1 37
students appear on the slides. They are prepared from pictures taken in the laboratorv where thev are workinz. Most of the experimental arrangements shown on the slides are the arraneements thev will be actuallv usinz The slides are made using a Sears Auto-126 camera and kodachrome-64 film. The tapes carry the voice of the professor in charge of the course. The purpose of the tapes is to give a theoretical background discussion and an overview of the activity. The students may listen to the tapes along with viewing the slides as often as is necessary for comprehension.Vhis has really been a big boost to creating interest, since understanding is a precursor of interest. The author does not mean to imply that this is the only place where something of this nature has been done. However, similar innovations have mostly applied to beginning courses in chemistry. Professor Meloan a t Kansas State University reported using individual tape recorders as a means of orovidine instructions for his senior-level students in analytical chemistry a t the American Chemical Societv Meetine in Seotember. 1970. in Chicaeo. The teachine of a ~ a l y t i ~ a l c h e m i was'a k r ~ big topic of dkxssion a t t h g meeting. Some companies such as Beckman Instruments, Inc., Sadtler Research Laboratories, Inc., and John Wiley and Sons, Inc., have similar programs in their libraries for rent or purchase. However, the unique aspect of the present program is that i t deals with apparatus and materials the students will actually be using in their own laboratory. I t is tailored to their needs. The first semester of the laboratory course deals essentially with the anatomy and use of the analytical balance, and calibration of the modules they will be using for synthesizing instruments in future experiments. The second semester is devoted to chemical experiments or studies. The chemical experiments are designed to make the students think and figure things out for themselves; hence, they are called studies. Each study may include two or more experiments designated to build knowledge in that area. Tables 1and 2 show a partial list of activities for each of the two semesters. The purpose of the modular approach to teaching analytical chemistry laboratory is two-fold: (1) to educate the student in activities that set analytical chemistry apart as a discioline: and, (2) to em~hasizethat it is the chemical svstem and measurements desired that dictate the experimental arrangement, instrumentation, and mathematics used in any chemical experiment. These goals, we feel, enable students to see the broad application of analytical chemistry. In an effort to achieve the first goal described above, approximately one-half year is spent doing calibration and related work. Instrument modules,4 manufactured and sold by A.R.F. Products, Incorporated, Raton, New Mexico, and all the pertinent volumetric glassware (flasks, pipets, and burets) are tested for accuracy and coded in a manner similar to that used by the National Bureau of Standards. The anatomy of the analytical balance and its use are taught, first, on the double-pan chainomatic type, followed by using a single-pan balance (the author calls this the "Moron's halance").,. ~~~~~. The Demonarration Osrilloirope, mant~farluredby the Sargent.\\'elch Srientifir Company, is used for introducing this instrument on a modular basis. It rnmes in five bnsir
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:'The students may use the materlal outside of class by appointment. 'These instrument modules were developed by A. R. F. Products, Inc., the National Science Foundation, and Dr. Galen W. Ewing (then at New Mexico Highlands University). The calibration experiments of some of the modules are adaptations of the ones suggested in Dr. Ewing's "Analytical instrumentation" Plenum Press, New York, 1966. 38 1 Journal of Chemical Education
Table 1. A Partial List of First Semester Activities
Statistical Study. PurPore: T o w i n experience in the use o f rtatirticai analvrir in reporiing scientific mearurementr. Electrical Measurements. I. The Potentiometer. Purpose: TO gain experience in the operation and use of a potentiometer. Electrical Mearurementr. 1 1 . The voltage Reference source. Purpore: To Calibrate and determine the performance characteriQiCI o f a voltage source module. Eiectrticai Mearurements. V. The operational Amplifier. PurPore: To determine the accuracv o f the direct current amolifier module, and t o study its integrating characterirticr. Electrical Measurements. V I I . T h e Wheatrtone Bridge and Thermistor Probe. p u r p o s e : ~ oG a y the performance characterirticr of the wheatstone bridge module, and t o determine the temperature coefficient of the thermistor Probe.
Table 2.
A Partial List of Second Semester Exoeriments
Preparation of a Saturated calomel Electrode. PU~POIB: T O gain understanding of the anatomy and criteria for a reference electrode; also, t o better understand h o w i t functions. An Oxidation-Reduction~chelometticStudy. Purpose: T O determine the formal potential for a given system, and t o study the effect o f certain chelatins agents on the formal potential for the samesyrtem. Also, t o ascertain the rtoichiometry of the complex formed. A Neutralization Study. I. Aqueous Soiventr. Purpose: T o compare the accuracy of titration data taken from the modular DH meter with that taken from the commercial
energy with matter. A C o n d u c t o m e t r i ~ - ~ h e r m o m e t tstudy ic
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P U I P ~ : TO obtain inforGatlDn on the quantitative separation of the c o m m n e n t r o f a mixture.
modules: The cathode ray tube, the vertical-and horizontal-deflection amplifiers, the pre-amplifier, and the sawtooth sweep generator. The students can clearly see how each module affects the electron beam as it is added to the cathode ray tube module. The parallelism between the nscilloscope and a television receiver plays no little part in contributing to the interest manifested in this activity, as evidenced by questions and discussion. The student learns the function of each instrumentmodule before i t becomes part of a complete instrument or complicated network. Since each module is designed to perform a particular function, the student can logically deduce why a particular module is needed in an instrument. The A.R.F. modules include such items as a voltage source, current source, operational amplifier, electrometer, dc meter, and Wheatstone bridge. Also, the student begins to understand why values measured in the class laboratory quite often deviate considerably from values found in the literature and generally used for comparison. The students are then in a position to write meaningful discussions explaining value deviations and sources of error. The temperature is a problem here in our laboratory (it is either too hot or too cold), so this has proved to be very helpful in that the students can handle, and thereby understand, a real source of error, since many experiments in chemistry have a temperature dependency. The second half of the year is spent performing chemical experiments which put these performance and calibration data into use. The first activity in this series is the preparation of a saturated calomel electrode, which is used in all subsequent activities requiring such a reference electrode. Other electrodes, such as plantinized platinum, platinum redox, and base metal electrodes, are made as needed. The
Universal Electrode Kit sold by the Kontes Glass Company, Vineland, New Jersey, is used as a source of prefabricated electrodes. They are neatly arranged in a very nice portable storage case. This experience has proven to be very valuable in helping students understand how an electrode functions. The chemical exoeriments are designed to achieve goal two, which is stated as: To emphasizethat it is the chimical svstem and measurements desired that dictate the experimental arrangement, instrumentation, and mathematics used in any chemical experiment. The instrum e n t ( ~ )required for a particular experiment may be synthesized from the modules. In some instances, the data collected from the modular instrument are compared with results from a commercial instrument (for example, the modular pH meter is compared with a commercial pH meter, or the Absorptiometer Module with the Spectronic-20). This nuite often eives~ the~ student added confidence in the perx ~ ~ formance of the modules. Using modular instruments develops within the student an awareness of the common features to be found in various instruments. They are able to logically deduce that certain requirements in any measuring system are fundamental, and also deduce why certain modules are used in almost every instrument synthesized. A written report including supporting graphs, either manuallv drawn or recorded, and a brief discussion of the underlyAg theory is required at the end of each activity. A statistical treatment of the experimental data, as far as is feasible, is also a part of the report. Students are given instructions on what must be included in each report; however, no "form" is issued. This type of "free" assignment provides, in general, an excellent clue to the type of student being dealt with. It is of interest to correlate the neatness and orderliness of such a report with the class performance of the student submitting it. There is almost always a positive correlation. In summary, a course in Analytical Chemistry Lahoratory has been designed that: (1) emphasizes the activities which set analytical chemistry apart as a discipline; (2) fo~
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cuses on the fact that the chemical system dictates the instrumentation and mathematics used in any chemical experiment; (3) provides experience in the preparation of a readable. meanineful written reoort. " . . which is a verv essential part of any scientific work; and (4) leads students t o a search of the literature for backeround information for a particular experiment, and in so doing broadens their general knowledge. The items listed above describe, in part, the kind of knowledge the author deems transferable. The speed with which instrument cabinets or consoles change in design is far too great for one to spend the time learning where the switches are located on a particular model of a commercial instrument. Realizing the function of any instrument that is designed for a particular technique, one can soon become familiar with the physical arrangement of console panel knobs. It is the author's belief that the modular approach is a meaningful one for all students of analytical chemistry, whether their aim is medical school, graduate school for becoming a professional analytical chemist, or becoming an analyst performing routine work. Once the principles are learned.. thev. can be used in manv different settinas, - . and therefore provide useable, transferable knowledge. Further information concerning the experiments used in this course may be obtained upon request from the author. The author also welcomes comments from colleagues. i l ) Harnmmd, GeorgeS., J. CHEM. EDUC.. ~1.558i19741. 121 Landis.V.J.. J. CHEM. EDUC..5l,561 (1974). 191 Reilby.A.L..J.CHRM. EDUC..51.67911972). (4) Howery,D. G.. J. CHEM. EDUC..49,155 (1972). i s ) K ~ ~ ~ ~ P ~ v . T . . J . CEDUC.49.629 HEM. 119721. (6) Mil1er.J. M.. M i l k d . W.. Noiron. G. V., and Scott, D. A J. CHEM. EDUC.. 50,708
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Volume 53. Number I , January 1976 / 39
