VOL.3, NO.2
A SETOF BORAXBEADSTANDARDS
189
A SET OF BORAX BEAD STANDARDS EARLER. CALEY,MONROBVILLE HIGH SCHOOL, MONROBVILLE, ORIO Teachers of elementary chemistry and qualitative analysis are frequently busy persons during the laboratory periods. Much of this activity consists in answering the same kind of questions propounded by as many different pupils as the laboratory contains. Much of this questioning is, of course, necessary and is a helpful part of the educative process. Some of it, however, especially the kmd involving the teacher's confirmation of the color of precipitates, flames, borax beads, and similar things, is needlessly repetitive and takes away much of the teacher's time that could be spent with more profit in other directions. Certain mechanical aids can be used as time-saving devices to remedy this difficulty. As a single illustrative example of this k i d of a teacher's aid, there is described here a set of borax bead standards which is to be prepared and hung up in a prominent place in the laboratory so that the pupils may consult it, instead of asking the instructor about the colors of beads that they have obtained. In addition to saving the teacher's time this device permits the pupils to consult a surer guide, Nature herself, for a check on their own work. It may be thought, a t first hand, that the only operations needed in order to prepare a set of borax bead standards are: to make the beads using a platinum wire and suitable metallic compounds, to let these specimens cool, and then to place them in a glass-covered cardboard box or container. In practice, however, i t is found that beads left in contact with the moisture of the atmosphere soon lose their luster and even their characteristic color. The beads must be preserved in small glass tubes. The entire process is therefore described in detail. A number of glass tubes about three centimeters long and one-half centimeter in diameter are first cut and sealed a t one end in the usual way. These serve as the containers for the prepared beads. The beads, themselves, are best made by using a blast lamp. By this means, beads showing perfectly the characteristic oxidizing and reducing colors can be prepared. Near the blast lamp should be placed a glazed porcelain evaporating dish, of large size, which must be perfectly clean and dry. The borax bead is then made in the usual manner, using a looped platinum wire and metallic salt solutions. When a satisfactory bead has been obtained, the wire holding it is tapped on the side of the porcelain dish, to detach the bead which rolls down the side of the dish and takes on a perfectly spherical shape. The bead thus formed should, a t once, be placed in one of the glass tubes, the other end of which is then quickly sealed in the blast flame. Beads prepared in this manner retain their original luster and color indefinitely. At least two beads for each metal should be prepared, one showing the color under oxidizing conditions,
the other, the color formed in the reducing flame. Other beads of each kind may also be made, if desired, showing the effects of different quantities of metal present upon the color of the borax bead. The set of borax beads, so prepared, should be mounted with suitable labels upon a card, or better yet, in a small glass-covered wooden case. In the latter case the tubes are conveniently held in place with cotton wadding. The use of laboratory standards, can, in this manner, be readily extended to other topics by the resourceful chemistry teacher. The use of standards is not only a time-saving device for the teacher, but is also desirable from the pedagogical standpoint. I t is all too easy for the pupil to get into the habit of continually asking questions about the colors and other qualitative aspects of substances he has prepared or obtained in tests. And i t is also easy for the teacher to get into the habit of affirming the pupil's results in this regard. In this way the pupil gets to rely upon the authority of the teacher instead of the authority of Nature; and it is the authority of the latter that the pupil must be made to rely upon if we are ever to hope to inculcate something of the scientific attitude and spirit, as one of the results of our secondary school courses in chemistry and other sciences.
