VOL. 6,No. 3
THE CHEMISTRY STUDENT
555
By the arrangement of the units on this chart, elements of one family are seen to he in the same vertical column. Thus we find fluorine, chlorine, bromine, and iodine in the number VII column. The elements in one column which have their melting- and boiling-point graph on the same side of their unit more nearly resemble each other than those which do not. The chart is completed with a legend in the upper right-hand corner and an index to the elements in the lower right-hand corner.
TINNING AND ZINCING
The following experiment may he used to demonstrate a method for plating protective coatings of tin, zinc, and other metals on iron. The article to be plated should first be well cleaned and then pickled in sulfuric acid sp. gr. about 1.66. It may then beplaced, afterwashing, in an ordinary Pyrex test tube with the right amount of tin or zinc. On top of the tin or zinc should be placed the flux to prevent oxidation. After the metal has been melted, a very satisfactory coating of tin or zinc should he found adhering to the iron. For a flux, ammonium chloride serves very well although tallow, zinc chloride, and palm oil may also he used.
STUDENT CONTRIBUTIONS Is your chemistry club carrying on some worthwhile project? Have you, yourself, an interesting chemical hobby? Have you devised an original chemical experiment or piece of apparatus? Have you built a working model of a chemical plant or a piece of chemical machinery? Have you a chemical collection of any kind? Tell us and other students about i t in an article of not more than one thousand words. If possible, illustrate your article with drawings or photographs, or both. In preparing your manuscript, observe the directions to authors set forth on page 408. Ten dollars will be awarded the high-school or undergraduate college student contributing the best item received on or before April 15, 1929. Five dollars will be paid for any other articles accepted for publication. Address your contribution to the Associate Editor, JOURNAL OF CHEMICAL EDUCATION, The Johns Hopkins University, Baltimore, Md.
