SEMIMICRO LABORATORIES RAYMOND R. CHELBERG and JOHN E. ANDERSON Michigan College of Mining and Technology, Sault Ste. Marie Branch, Sault Ste. Marie, Michigan
THE semimicro methods in use in general and organic, as well as qualitative, chemistry laboratories a t this branch college have proved economical of time, space, and materials. Dispensation of reagents in drop rather than in milliliter quantities effects marked savings in time and space, since need for refilling 30-ml. dropping bottles is no more frequent than that required to refill the 300-ml. bottles required on the macro scale. Changeover from macro to semimicro scale reduces, perhaps tenfold, space normally required for storage, dispensation, and manipulation, an item not to be ignored in schools with space problems. Teachers who have visited the Sault Ste. Marie Branch laboratories have suggested a published description of the novel aspects of one of the laboratories as a possible aid to highschool and college instrnctors who may wish to convert from macro to semimicro laboratories with the view in mind of cutting costs, saving space, and training their students according to the present trend. The plan of the general, organic, and qualitative laboratories is about the same. Quadruplicate sets of reagents in 250-ml. bottles are strategically located at the four corners of a laboratory of large size, duplicate sets sufficing for smaller ones, such solutions serving for those few experiments which call for more than drop quantities. Two hoods, each with 61/2 sq. ft. of working area a t two ends of the laboratory, are equipped with ordinary pipe manifold and hard-rubber stopcocks and water traps for dispensing Hi3 from a cylinder containing 20 lb, of gas, located midway between the two hoods to minimize piping. Since the cylinder had to be in the laboratory, a glassed-in box equipped with a padlock was built around a reduction valve, thus ensuring proper regulation. The usual metal stopcocks tend to corrode and "freeze" or become difficult to turn. The total investment, including cylinder, reducing valve, piping, and stopcocks did not exceed $100. Open shelves, located a t the ends of the laboratory, or in the middle along the wall, are used for supporting duplicate sets of solid chemicals. For weighing, two side shelf balances of 0.1 g. sensitivity are provided for each table. As a lwxury item, an adjoining room is supplied with analytical balances. Careful instruction in, and supervision over, their use are given by the staff members to each student. All students,
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except those in quantitative chemistry who have their own balance room, use these. The most unique feature of the semimicro laboratory is the reagent rack, a photograph of which is given. The design consists of a duplicate set of 60 reagents in ll/rin. square, 30-1111. Barnes' bottles. Each set is in two rows, locked in place by a 43-in., two-section dowel to facilitate removal of bottles for cleaning. Bottles may be refilled in situ, if desired. Smaller racks are of identical design except for length. Cations, anions, and reagents for their analysis require less space. Blocks 173/a in. long, 33/4 in. wide, and 1 1 / 2 in. high, having holes 2 in. in diameter and 7/s in. deep, hold in. in diameter and 70ml. capacity, six round bottles 11/2 which contain the highly concentrated acids. One of these blocks accompanies each large rack and, like the rack, serves a minimum of four students. For the Barnes' bottles containing the more frequently used acids and bases, a box 8'/2 in. by 33/4 in., and in. in depth, inside measurement, is provided. A longitudinal partition 3/a in. in thickness and I/* in. high separates the duplicate sets of bottles. One of these containers takes care of two adjacent students. A fourth useful piece of equipment is a block holding the test tubes, filter tube, and glass rods needed for semimicro work. The block is S1/z X 2 X 13/4 in. Holes, 16/le in. in diameter, alternating with some llrin. ones, are bored to a depth of 11/4 in. along one edge. Seven 'lrin. holes occupy the opposite edge,
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while the center is lined with L/4-in. holes for the glass beakers, etc., is a case in point. The chemicals needed rods. These rods serve as supports for draining or are nearly all a t his bench, thus reducing trips to the drying test tubes and for tamping down the filter dispensary window. This results in the elimination plugs. This block has proved more convenient than of waiting, visiting, and attendant confusion. the commercial racks. How much time is actually saved has not been Siice the individual student needs comparatively determined. However, the three-hour laboratory pelittle equipment, he has more working space. The riod, which was instituted to replace the previous replacement, by the simple but effective filter tube, four-hour one, has apparently affected neither the of the bulky filtering apparatus with ring stand, funnels, quantity nor quality of the work.
