UNDERGRADUATE RESEARCH PROJECTS IN QUALITATIVE ANALYSIS' BRUCE McDUFFIEa Emory University, Emory University, Georgia
ONE
of the interesting aspects of laboratory instruction in qualitative analysis is the amazing number and variety of questions that are asked by the students. Granted that these questions often arise from the misreading of directions or from other careless mistakes, many of the questions deal with chemical phenomena that the students, and often the instructor, cannot explain. It is to answer some of these questions, as well as to make improvements in the procedures, that we have assigned projects of a research nature to approximately 175 undergraduates in qualitative analysis during the past four years. This number of students represents about 19 per cent of the total enrollment in the course for that period. Qualitative analysis a t Emory University is a onequarter course which follows a two-quarter sequence of general chemistry. There are three lectures and two three-hour laboratory periods per week. The laboratory work includes the analysis of solutions for cations (about 13 periods), the analysis of solid salts for anions (about three periods), and the identification of simple salts (about two periods). At present the special research projects are not an integral part of the lahoratory work, but are reserved for students who finish the required work ahead of schedule and desire to devote one or two periods to such a project. In a previous year the completion of a special project was incorporated in the regular schedule and required of all students. A student is encouraged to select a project based on his own observations or on a difficulty that he has encountered with a particular step in the procedure or with a particular unknown. If a student has no suggestions the instmctor usually has plenty, from his own observations or from the observations and questions of other students. It is often desirable for several students to work (separately) on the same problem. Once a particular project has been selected, the instructor outlines with the student the objective and the plan of attack, then the student proceeds with the experimental work, taking notes as he goes and conferring with the instmctor when the need arises. As the work progresses and new aspects of the problem arise the student often goes ahead on his own, devising new experiments. Finally the student submits a report of several pages consisting of: (1) a statement of the problem, (2) a 1 From a paper presented a t the 28th Annual Meeting of the Georgia Academy of Science, Athens, Georgia, April 27, 1951. Present address: Department of Chemistry, Wa~hingtonand Jefferson College, Wmhingtan, Pennsylvania.
detailed summary of all experimental work, including usually a table of data, and (3) conclusions or recommendations. The following list of typical research projects will give some indication of the scope and possibilities of this feature of the qualitative analysis course.
Sodium, Potassium, and Ammonium Ions Sensitivity of the flame test for sodium. Comparisons of various light filters far tho ~ot,sssiumflame test. Sensitivity of the ammonium ion test using sodium hydroxide. Investigation of the yellow precipitate obtained when the ammonium ion test was performed on a solution containing the cations of Group I.
Cation Group I Precipihtion of lead chloride under various conditions.
Cation Group II Optimum acidity for precipitation of Group I1 sulfides. Use of sodium hydroxide p l u ~hydrogen sulfide t o dissolve Group IIR sulfides. Effect of nitric acid on the precipitation of lead sulfate. Sensitivity of the test for bismuth. Study of the detection of cadmium in the presence of copper using the sodium chloride-hydrogen sulfide methad. Study of the test for mercuric ion with stannous chloride. Amount of washing needed to remove chloride ions from srsenious sulfide, prior t o the test for arsenic. Development of a specific test for arsenic. A simple confirmatory test for antimony, based on the reprecipitation of antimonous sulfide. Investigation of the red-hrown solution formed when silver ion is added to traces of stannous ion.
Cation Group III Study of the incomplete precipitation of soms Group 111 nnlfides. ~. Effect of acidity on the reaction of hydrogen ~ulfidewith ferric solutions. Effect of impurities on the color of aluminum hydroxide. Study of the wine-red color obtained on dissolving.s. mixture of hydroxides in ohlaroaretie acid. Ob~ervationson the mecioitation of hinc sulfide. and ~ossible interferences in the test for sinc. Study of the complex formed h y chromic ion in solutions containing ehloroacetic acid. Precipitation of basic cobalt chloride as a test for cobalt. Development of a simplified procedure for the detection of manganese and iron. A study of difficulties enoonntered in tho test for aluminum with aluminon reagent.
Cation
'I
Effect of ammonium chloride and ammonia concentration on the separation of Group I V from magnesium. Sensitivity of the procedure for the detection of calcium.
JANUARY, 1952
Anions Test for nitrate in the presence of nitrite. Test for acetate in the presence of iodide. Occurrence of sulfate ion in lead sulfide unknown. Occurrence of sulfate ion in sulfite unknowns. use so~utionsto sepssrtte the silver halide group, Silver ion as a general reagent for the anions.
Miscellaneous Quick t,est for the potency of hydrogen peroxide solutions. Standard names for the colors of precipitates and solutions. Qualitative analysis of miscellaneous substances, such as coins, rocks, clay, soit drinks, and vitamin pills.
has heen our experience that enjoy this taste of research and that it provides a fitting climax to
37
the first year's work in chemistry. Of necessity the unit of work accomplished by any one student will be quite small, but taken together these units of work have formed the basis for many changes in the scheme of analysis and have in several cases laid the foundation for more advanced research. Furthermore, as in all research, students learn the importance and the satisfaction of a systematic and imaginative approach to the problems. TOecho the words of R. E. Kirk: "But is this research? P e r h a ~ snot to the teacher. but it is real -r -e search to the boy! And it is a real &aching tool!"3 3 KIRK,R. E., J. CHEM. EDUC., Q, 280 (1932).
