THE TEACHING OF QUALITATIVE ANALYSIS IN SECONDARY SCHOOLS*
Under suitable local conditions a half-year course in qualitative analysis, following a year of general chemistry, can make a distinctive contribution to the science program of the secondary school and can serve to supplement and reenforce the course in general chemistry in the attainment of certain generally recognized objectives. Some Distinctive Features of Qualitative Analysis Some of the distinctive features of qualitative analysis may be briefly outlined as follows: 1. It is inherently a laboratory course. In qualitative analysis, to a greater extent than in any other science course commonly offered in the high school, the pupil learns through his own activities. 2. Analytical work demands greater continuity of effort, more sustained attention t o details. The pupil soon learns that what he does a t one point in his work is significant not only in itself hut also in its possible effect upon the work which follows. He must be on the alert all the time and follow things through t o the finish if he is t o be successful. 3. Another distinctive feature of qualitative analysis is its automatic emphasis upon the value of system and accuracy in procedure. Slipshod work brings its own inevitable penalties, systematic and careful work reaps its sure reward in the satisfaction which comes from the correct solution of a concrete problem. 4. I n qualitative analysis the pupil is independent in his laboratory work t o a greater degree than is possible in most science courses. Each student is working on a problem of his own and must stand or fall on his own efforts. I n the nature of things he must do his own work and draw his own conclusions. 5 . An experience of some twelve years in the teaching of qualitative analysis to high-school students has convinced the writer that this type of work catches and holds the interest of the student in a distinctive way. Every "unknown" is a challenge to his ability t o follow up clues, gather evidence and draw conclusions, as does the sleuth in the detective story. In how many courses must teachers meet requests from pupils for extra working time in the laboratory outside of regular hours? To the teacher of qualitative analysis this is a common experience.
* Contribution to the Symposium on The Teaching of Analytical Chemistry, held by the Division of Chemical Education, at the 75th Meeting of the A. C. S., April 5,937-89 (Aug., 1928). 17-18, 1928, at St. Louis, Missouri. See THISJOURNAL,
VOL.6, NO. 3 TEACHING QUALITATIVE ANALYSISIN SECONDARY SCHOOLS 487 Objectives of High-School Chemistry and How Qualitative Analysis May Help Attain Them What are the objectives of high-school chemistry for the attainment of which the study of qualitative analysis may supplement and reenforce the course in general chemistry? Of the objectives listed by the Committee on Chemical Education of the American Chemical Society, the following are selected in this connection: 1. To show the senrice of chemistry to the home, to health, to medicine, to agriculture, to i n d u s t r y i n a word, to show the service of chemistry to the nation. Probably most of us who teach qualitative analysis would have to plead lack of time as our excuse for not doing as much as could be done along the line of this objective. There is a wealth of illustrative material with which to show the valuable services which are daily being rendered through practical applications of qualitative and quantitative analysis. 2. To train the student i n keen observation and exact reasoning. Observation is motivated in analytical work. The extent to which the student is brought to exercise his powers of reasoning depends largely upon the way in which the course is conducted. 3. To build upon earlier science courses and knit them together. In an elementary course this applies chiefly to building upon the course in general chemistry, particularly with respect to such topics as solutions, reactions of acids, bases, and salts, oxidation and reduction, ionic theory, and methods of separation based on differences of solubility. 4. To help pupils to find themselves-to discover whether they have an aptitude for further study i n chemistry or applied science. Of the objectives cited by Dr. S. R. Powers in a list prepared by him a few years ago, qualitative analysis may claim to help toward the attainment of the following: 1. To contribute such specific ideals, habits, and concepts as those of accuracy, achievement, persistency, open-mindedness, honesty, cause and effect, which are essential to the study of science. 2. To develop system, order, neatness, and possibly other attributes to the end that they may function in ordinary life. 3. To give such training as will result in increasing respect for the work of recognized experts.
These objectives may well be among those set up for qualitative analysis in the secondary school. In an article on "The Cultural Value of Qualitative Analysis" [THIS JOURNAL, 4, 355 (March, 1927)l Edgar J. Witzemann states: What is wanted is a type of training of this sort that is available for large numbers of pupils at an early stage of their mental maturation. Something is wanted in which it is possible for the pupil to test and retwt in his own way and to his own satisfactionthe
utility and logic of the method that he is being taught. Something in which his teacher, if he wishes, can dissociate himself temporarily from his position of superiority and approach the problem in the same spirit as the pupil. The material should he well within the scope of the powers of the pupil so that he need not rely too much upon authority.. . . .For such purooses as these in training in the scientific method, it is the writer's opinion that qualitative analysis offers advantages over all other subjects in the curriculum, other things being equal.
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Effect of ~ i ~ h - ~ c h o o l ~ ~ u a l i Analysis t a t i v e upon College Chemistry
It would be of interest to know what effect, if any, the study of qualitative analysis in high school may have upon the student's success in beginning college chemistry. During the years 1020-27, two hundred Chemistry studied i n the high school Gen. ehcm. ' / a yr. None Gcnersl chem. of qual. anal.
+
I. Enrolment in college chemistry Number enrolled in university Number taking college chemistry Per cent taking college chemistry
41 12 29.3%
11. Average rating in college chemistry (2) 78.0 Group A (8) 55.0 Group B (2)55.5 Group C (12) 58.9 All groups, mean 63.5 All groups, median
III. Rated 80 to 100 in college chemistry Group A Group B Group C All groups
85 41 48.2% (12) 80.3 (12) 71.7 (17)61.5 (41) 70.0 70.0 7/12=58.3% 1/12= 8.3% 1/17= 5.9% 9/41=21.9%
115 85 73.9% (42) (30) (13) (85)
85.7 74.2 68.0 78.9 80.0
34/42=80.9% 9/30=30.0% 1/13= 7.7% 44/85=51.8%
N. Failures in college chemistry None None None Group A 1/12= 8.3% 1/30= 3.3% 3/8=37.5% Group B 2/13=15.4% 1/2=50.0% 4/17=23.5% Group C 3/85= 3.5% 4/12=33.3% 5/41=12.2% All groups V. Comvrison of students who were rated 80 to 100 in general chemistry in high school Numher Average rating in general chemistry in high school Average rating in college chem74.7 80.0 istry VI. Comparison of students equated a s to I. Q. Number 18 18 Average I. Q. 116 116 Average rating in college chem80.2 87.4 istry
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islry? Y e s , 14. If so, for hmu many weeks? 10 t o 16 wks., 6; 5 to 8 wks., 4; 4 wks. or less, 4. 10. Length of laboratory periods in gualitativc analyns? Average, 80 min.; most common (12 out of 28), 80 t o 90 min. How many of these $eriods per week? Average. 3.5. 11. Minimum length o j lab. period which you consider satisfactory for qualitative analysis? Average, 89 min. ; 14 out of 28 say 90 min. 12. Length of period for lecture, recitation, or discussion? Average, 51 min.; 40 t o 50 min., 16; 60 min., 7; 70 min., 2. How many of these periods per week? Average, 2+. 13. How many weeks are devoted to analysis of unknozun solutions (detection of cations only)? Average 11 for half-year course. 14. How many weeks are devoted to a m l y s i s of unknown solids (detection of cations and anions)? Average, 7 for half-year course. 15. Indicate what cations are omitted from or added to the jollowilrg list, i n your course: Ph, Ap, Hg+, Hgt+, Cu, Bi, Cd, Sb, As, Sn. Co, Ni, Fe, Cr, Al, Zn, Mn, Ba, Sr, Ca,Mg, Na, K, NH,. Replies show that prevailing practice fm half-year course is t o eive the cations listed above. One adds Li. 1 adds Pt and Au. 1 omits Na.. K.. NH,. 2 omit Sb, As. Sn. 16. Check those,. if . anv, . o.f the .follomin~ .anions which are omitted i n YML7 course: arsenete, arsenite, borate, cyanide, fewicyenide, fenocyenide, .fluoride, nitrite, oxalate. silkate, sulfocyanate, tartrate, thiosulfate. A majority of all schools reporting omit anenate, arsenite, cyanide, fluoride, sulfocyanate, thiosulfate. Given in the course: oxalate, 22; tartrate, 22; borate, 21; silicate, 20. 17. Of the following topics, check those which you stress i n recitation periods. ( a ) Methods used in the scheme of analysis. ( b ) Reasons for the oarious deps i n analytical procedure. (c) Equation writing. ( d ) Law of mass action. (e) Ionic theory. ( f ) Common ion effect. (g) Solubility product. Replies show that a majority of all schools reporting and nearly all schools giving a half-year course emphasize topics ( a ) , (b).
(GI, (4. Professor Frank believes in the plan of giving qualitative analysis as a part of the second semester's work in general chemistry in the high school. In his book on "Teaching First-Year Chemistry" he says: There is no other course in the realm of science which can arouse the interest of the student and enforce his resped like qualitative analysis well given. The giving of qualitative analvsis as the second semester's work will do away with the monotonous routine which mast elementary courses settle into during the second semester. . . . . .Instead it will make the work of the second semester even more interesting and alive than the work of the first semester.
The writer has never attempted to teach qualitative analysis as a part of the second semester's work and is not qualified to discuss the advantages and disadvantages of this arrangement. On general grounds i t seems questionable whether the important topics in general chemistry which must necessarily fall into the second semester will leave sufficient time for a
worthwhile course in qualitative analysis. However, the reports from teachers who are trying this plan indicate that they find i t satisfactory and expect to continue it. Apparently these teachers find it feasible to have their classes carry out some work in qualitative analysis in connection with the study of the metals, making such variations from the usual order of the metals as the situation demands. The replies to the questionnaire did not bring out adequate information as to just how much actually is accomplished in analytical work under this method. A full half-year is not too long for a thorough-going elementary course in qualitative analysis. Time must be allowed for discussions to clarify the student's understanding of the reasons for the various steps in the scheme of analysis which he is using and for the precautions to be taken a t various points. Unless some check-up is maintained on this matter, both in recitation and in the laboratory, the student is likely to fall into a rut of routine, a mere following of directions-a kind of mechanical performance unworthy of the name of analytical work. There will not he time for more than the fundamentals of the theoretical background and probably not much of this could be successfully undertaken with high-school students even if time were available. The writer's practice in regard to item no. 17 of the questionnaire is in line with that of the majority who replied. Some Suggestions In deciding upon the best use of available time, the teacher of qualitative analysis has to consider, among other things, the following questions: 1. Are preliminary experiments with salts of the individual metals of sufficient value to justify the time required for them? The writer agrees with those who maintain that preliminary experiments preceding each group of cations should be limited to reactions which will actually be used later in the scheme of analysis. These experiments should be motivated by making the student realize their usefulness: if he gives proper attention to the preliminary reactions, noting the color and form of precipitates and so forth, he may he more than repaid later by time saved in actual analyses through recognition of the absence of certain metals and consequent shortening of the procedure. 2. Should the student go through the analysis of a known solution in a given group before attempting an "unknown" of that group? This practice gives the student an opportunity to find out whether he really understands the directions so that he can translate printed words into intelligent action. It also enables him to find out where difficulties are likely to be met and how to surmount them; where mistakes are likely to occur and how to avoid them.
3. Should a time limit be set for each analysis? Some experienced teachers have reported using this scheme to advantage. Most texts require the exercise of the teacher's judgment as to selection and adaptation of the material to be used. Straightforward, clear-cut' directions for procedure are needed, and if there are swampy spots in an otherwise good book the teacher may do well to bridge these over with directions prepared by himself and adapted to the course as he wishes to give it. It seems unnecessary to emphasize the importance of the teacher's skill and resourcefulness as determining factors in the success of qualitative analysis as a secondary school subject. A group of wide-awake high-school students out on the trail of the "unknown" under an enthusiastic and resourceful guide can make any chemical laboratory a place of lively activity and wholesome comradeship, where joy in the quest abounds!
