VOL. 6, NO. 6
HIGH-SCHOOL PROJECTS I N CREWSTRY
1143
the subject. No phase can be studied in much detail in the regular class work. The semester project seems to help solve some of the numerous difficulties met by a teacher of high-school chemistry. 1. It allows the student to pick out some interesting aspect of the subject and to study it in more detail and a t greater length than is possible in the regular classroom work. 2. It enables the superior student to do a great deal of work a t odd times when the remainder of the class is completing an experiment, a set of problems or a quiz. If the student is able to proceed alone he should be encouraged, if not he should be guided and assisted. 3. It works toward more correlation with other departments in the school than is usually practical otherwise. The building of a photographic printing box or a display rack can best be done in the wood shop. The lettering of signs and the making of posters offers the student a chance to use his knowledge gained in art and drawing classes. The writing of long, carefully prepared papers and reports requires the pupils' best use of principles learned in English classes. The exhibits serve to advertise the chemistry classes. This should not be overlooked. Parents desire and have a right to know what the student is doing. Projects and exhibits afford a method of doing this in a satisfactory way. Prospective pupils may become interested. If school exhibits are to be made a t some local or country fair such reports accompanied by exhibits are valuable.
Physico-Chemical Investigations upon Radium. The increased demand for radium preparations for use in the cure of certain diseases has caused attention t o be directed t o the supplies available from the Belgian Congo. It has apparently been overlooked that the element was first discovered by Prof. and Mme. Curie in the pitchblende deposits of Jichymov (St. Joachimsthal) in northwest Bohemia, where the isolation of radium products has been resumed since 1920. In the Collection of Ceechoslavak Chemical Communications (January, 1929). Prof. J. Heyrovskf. and S. Berezickl describe the application of the dropping mercury cathode methods for determining the deposition potential of radium, which is found to be 1.718 volts. The deposition potential of the element in the presence of barium and other salts was also studied, using preparations containing amounts ranging from 14.6 per cent of radium t o a preparation containing 97.3 per cent of radium chloride. I t is found that the difference in the deposition potentials of the alkaline earth metals are great enough to permit of the deposition of each of them being followed in their mixtures. Traces of radium are noticeable in any amounts of calcium or strontium solutions, even in the presence of alkali metals. The deposition of radium becomes indistinguishable, however, when the ratio of barium to radium exceeds 10 :l. Traces of barium are discernible in solutions of $1 the alkalis and alkaline earths. The application of the polarographic method with the dropping mercury cathode to the determination of the solubilities of sparingly soluble salts has also been found to give ~ n c a r d a n tand satisfactory results.-Nature (London), 123, 296 (Feb. 23, 1929).
