Advantages of Semimicro Technic & Teaching Qualitative Analysis1 PAUL ARTHUR, J. A. BURROWS; 0. M. SMITH, a n d EVERETT L. ADAMS Oklahoma Agricultural and Mechanical College, Stillwater, Oklahoma
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MONG the most frequent questions asked by prospective users of semimicro technic is the allimportant one concerning the probable expense involved in changing from the macro to the semimicro equipment. An inusual ariangement of laboratories in the chemistry department at Oktahoma Agricultural and Mechanical College has enabled this department to keep accurate records, over a period of four years, for the semimicro qualitative analysis course. The analytical procedure used involved the customary hydrogen sulfide separation; consequently, it was possible to get laymen's opinions on the nuisance created by the use of this reagent. The experiences a t this college are described here in the hope that the iuformation thus furnished will he useful to others. The costs for such a course are very conveniently divided into two groups: (1) those which would he necessary in changing from the macro to the semimicro procedure-the starting costs, and (2) those necessary to maintain the c o u r e t h e current costs. The actual costs involved in equipping the laboratory a t this college for the course in semimicro qualitative analysis are given in Table 1. TABLE 1 Srranvo Cosrs
(lor 20 rtudents) Appnrntus kits at $5.60 Reagent blocks end vials (5 sets) Dropper bottles for test ~lolutionslor the side shelf Burners Centrifuges, two at 817.50
Cost per student Maem apparatus (returned to other courses) Saving on msintenanee of HtS and h d system
S112.M) 26.20 10.32 11.00 35.00
importance, is that of the running expenses. Careful accounts, covering eight semesters, with an average of 40.6 students taking the course each semester, give the averape results tabulated in Table 2.
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TABLE 2 Crmsenr Cosrs pen Sslaesra~ (for 20 students) Reagents and stock solutions Laboratory upkeep charge Student breakage and non-returnable at 82.23
15.40 1.40 44.60
$51.40
Total Cost per student
2.57
These figures, again, are based on twenty students. It will be noticed that the student breakage and the non-returnable item is the only costly one in the list. The current laboratory costs, exclusive of gas, water, and electricity, average only $2.57 per student for the whole course. Though the question of expense is quite important, no discussion of semimicro methods of teaching qualitative analysis is complete without considering some of the other features of such a course. A description of the arraueements used at this colleee azain will serve to bring oui some of these features. ~Yhequalitative analytical laboratory here is located in a large room on the third floor of a building, the remainder of which is occupied by the music department! The equipment in
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9.78 386.00
Undetermined
These figures cover equipment for twenty students except as otherwise indicated, and are based on the assumption that the department has none of the equipment already in stock. To make the picture even clearer, Table 1 includes also the cost of equipping an equal number of students with the apparatus which was used a t this college when the course-in qualitative analysis was taught by macro methods. Whcn the change in methods was made, all of this macro equipment was absorbed in other courses; EQUIPMENT POR SEMIMICRO QUALITATIVE ANALYSIS consequently, the change actually resulted in a saving of over $190 for each twenty students, during the f i s t the room is of surprising simpliaty. There is a long year. cost question, which is of even greater trough along the side of the room with water faucets The the trough to permit its use for washing appara' Much of the material in this article was presented in a paper along tus. plain tables with tops 4 feet by 20 feet, of before the Division of Chemical Education at the lOlst meeting just sufficient height (30 inches) to permit the students of the A. C. S., St. Louis, Missouri. April 9. 1941.
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to sit on ordinary chairs and work comfortably, serve as laboratory desks. The tables are equipped with gas, but not with water. The view across the table is unobstructed, since only large, flat, reagent blocks, each containing seventy reagents in vials, are on the tables. The liquid reagents and solutions are in 3-dram vials equipped with Barnes' type droppers; the solids are in one-dram vials fitted with ordinary stoppers. Each of these reagent blocks serves four students, two on each side of the table. Acids and bases are in oneounce bottles in smaller blocks, two of these being placed by each large block. Each student is provided with a hydrogen sulfide generator of the Aitch-Tu-Ess type. Test solutions and a few of the less stable reagents are the only chemicals not within easyreach of the seated student; consequently, moving around the room is reduced to a minimum. There are neither hoods nor special ventilating equipment in the room; yet the other classes in the building have, as yet, made no objection to the practice of the usually very objectionable qualitative analysis. Two electrically driven centrifugesz and a large bottle of distilled water
complete the equipment of the laboratory. The maximum capacity of this laboratory is thirty students, in a space which would ordinarily have accommodated not more than twenty students using the macro technic and apparatus. The teaching value of semimicro methods has been pointed out by many teachers of qualitative analysis, but the students themselves are the best source of information on this subject. Conversations with stndents, two or three years after they had taken this course, have indicated that the great respect for cleanliness and careful technic taught in the semimicro course made them feel that later courses were sloppy and clumsy in comparison. The realization that bulk is not important is one thing that seems surprising and interesting to most students. The course is quite selfmotivating in practice; and requests from students who have had the macro course for permission to take the laboratory part of the semimicro course are by no means uncommon.
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These centrifuges may be obtained from W. Edmund Fish.
P. 0.Box 414, West Lafayette, Indiana.
