THE USE OF WORKING DRAWINGS IN A LABORATORY COURSE IN GENERAL CHEMISTRY The principal motive in the laboratory part of a course in general chemistry of today is probably that of teaching the student to do scientific investigation on an elementary scale. This is particularly true if the instructor keeps this unit of the course slightly in advance of the work of the class-room. There are some who still believe that laboratory exercises allow the student the opportunity of verifying the well-known elementary facts of chemistry for himself. Regardless of which of the two kinds of pedagogy we individually follow, we are doubtless in agreement that the student has opened for him the gates permitting the development of his powers of observation and the drawing of conclusions therefrom. All of this is done under the careful guidance afforded by the instructor and the laboratory manual. Simultaneously the student has occasion to exercise his skill in the construction and manipulation of the appropriate apparatus for the conductance of his investigations. Herein lies one of the universally experienced difficulties in laboratory courses. Generally speaking, the manipulative part of the instmction, although brief, is sufficiently complete. Usually the apparatus is shown in scaled and lettered diagram accompanied in the paragraphed part of the instructions by a description of the correspondingly indicated parts of the diagram. In short, i t is the scheme handed down from the days of alchemy and probably earlier. If the architect of today used such a cumbersome and time-killing layout of a modem chemistry building, additional foremen would be required in the construction of the plant. Instead he furnishes the contractor with a working drawing of the project, containing the maximum number of specifications, thereby saving paper and time in his own laboratory and time for the contractor. The likelihood of getting the desired structure is also increased. It is now a common practice to have the students, in any of the fundamental courses in chemistry, construct a wash-bottle (or flask) as one of the first exercises. The manual contains a scaled drawing of the finished product and ample descriptive detail of the glass manipulations involved in the making of same. Quite a few teachers give the student some additional aid by putting a t his disposal, for critical inspection, an actual sample. Every teacher of chemistry will readily recall that the majority of the wash-bottles presented by the class were not of a quality worthy of exhibition, although they may have served the purpose for which they were intended. In 1922, a t the University of Wisconsin, the writer was giving instruc-
tion in general chemistry to engineering students and i t occurred to him that the spirit of their chosen profession might be furthered by having the bottles made to conform to specifications as given in a blue-printed working drawing. The improvement in the product was very marked. Previous to 1923 the Division of General Chemistry of the Ohio State University supplied each student (in addition to the instructions in the manual, with a square of asbestos board ruled so as to give the angles of the two major bends in the bottle. In making the bends, the student heated the glass to the proper plasticity, placed i t on the asbestos board and bent it to the angle given. When bent while in close contact with the board, the glass is less likely to sag a t the bend. The ruled square has since been augmented by the scaled drawing, with dimensions, with the result that less than 15y0of the wash-bottles are now returned to the students because of faulty proportions. There is also manifest t h e much desired uniformity in product. Figure 1 is a reproduction of the 81/z*X 11" drawing furnished the student. A tolerance of 5y0 is usually allowed. The mlings on t h e a s b e s t o s board are replicas of the F1g. 1 center lines FF' and GG'. The idea presented herein is rapidly being extended to the other exercises involving set-ups in the elementary chemistry courses a t this university.
