CORRESPONDENCE To the Editor
The semi-micro course in qualitative analysis was first offered a t Wayne in the fall of 1937. Semi-micro analysis has several distinct advantages over the macro system. Not the least of these is the interest of the students in the technic nsed. Work'mg with small quantities, our students develop good habits of careful handling of samples and reagents, as well as learn the value of extreme cleanliness in the care of glassware. Another distinct advantage is the economy of the course. Filter paper, an item of considerable expense in a qualitative analysis course, is not used. Filtering, the tedious time-consuming and wasteful process in.an analysis course, is eliminated. The separator, a new type of electric centrifuge, in a few seconds separates precipitate and filtrate most efficiently. Breakage is minimized and smaller test-tubes (75- and 100-mm. diameter tubes are used), thirty milliliter casseroles, small dropping bottles and beakers also represent a smaller original cost. Since smaller quantities of reagents are nsed, the saving in chemicals is obvious. Also an important advantage of semi-micro is the very apparent reduction of obnoiious gases in the laboratory. A few milliliters of solutionrrequire also a similar small amount of hydrogen sulfide, still a neces-
sary evil in qualitative analysis. Small individual generators are used with a source material which ceases to react as soon as the applied heat is removed. Precipitation of sulfides is easily and rapidly accomplished with a minimum of hydrogen sulfide escaping into the air. The possible quantities of other gases such as hydrogen chloride, ammonia and nitric acid are also diminished to a very great degree. Very little new equipment has been necessary for this change. Most of that which has been purchased is of a permanent nature, and glassware replacements are few and inexpensive. During the first semester, one separator of the solid aluminum head type, with spaces for four tubes, and the necessary tubes were purchased. The next year test-tube racks, 50-ml. Erlenmeyers and individual dropping reagent bottles replaced the larger sized bottles. The addition of small monel spatulas, bath-racks, a few spot plates and casseroles have completed, with other equipment used.also in other courses, the equipment for each student. In conclusion, we feel the semi-micro qualitative analysis course is most satisfactory for the teaching of chemical principles and methods of technic. It is most economical. It is interesting and stimulating to both students and teacher.
