--
which arc uwxdly included in a course in introductory chemistry. Specid attention is paid, however. to the advance. of the part ten years in the subatomic field. The usual order is followed: H, 0. Adds. Barer, Water, S. Halogens, N, P, As, Sb, C. s i , and B , followed by the metals. The subtopics are: History, Occurrence. Preparation. Chemical and Phyrieal P~lopertie and Use.. Emphadr is placed upon the mineralogy 01 the important elements. In an appendix are table of physical
and chemical units, with conversion fadore, and a table showing the important geologic perid. with their characteristic sediments and plant and animal life. While if could not serve alone as eithv a text or a laboratory manual. this little outline would make an ucellent guide for a review of clemeotary inorganic chemistry.
Chromium Improves Printing Plates. Better looking faces on our dollar bills as well as great saving to the government is achieved by a recently developed process of making electrolytic plates. Experience at the U. S. Bureau of Engraving and Printing has shown that by the application of a thin layer, only l/sma inch thick, of chromium to electrolytic plates used for printing paper currency, the life of the plates is increased to over twice that of case-hardened steel plates, and several times that of the nickd-faced electrolytic plates prior to the application of the chromium upon them. This increased service is due to the extreme hardness of chromium, the hardest metal known. Chromium plating has long been known to be possible, but until recently it has not been commercially practicable. Considerable research was required to develop and adapt it for this purpose. This study was conducted by H. E. Haring of the' Bureau of Standards. According to Dr. William Blum of that Bureau, subsequent tests have shown that chromium plating is likewise valuable on other types of printing plates, especially those used for long editions, such as on soap wrappers, cartons, labels, etc. I t will also probably be useful on dies and gauges where extreme hardness is required, and may obviate case hardening them. Further researches such as are being conducted by the Bureau of Standards and by numerous commercial laboratories, will no doubt lead to still more extensive applications of chromium plating, including those where its resistance to tarnish as well as its hardness will be valuable.-Science Semice Why Flour Should Not Be Ground Too Fine. Flour ground too fine does not make good bread. While millers have always been aware of this fact no one seems ever to have determined upon what the poorer quality depended. Accordingly. Drs. C. L. Alsberg and E. P. Griffing, two biological chemists of the Food Research Institute at Stanford University, have undertaken a ,series of experiments to answer this question. They have found that in over-ground flours the starch granules are injured so that carbon dioxide is given off a t first instead of gradually throughout the whole baking process. This gives a bread that "rises" too fast at first and will not "come up" in the oven. The gluten, also, of very'finely ground flours is injured. Gluten is the substance in dough that gives it elasticity. Without this elastic property the dough is very difficult to knead. Any housewife knows that dough that is "crumbly" rather than "stretchy" will not make good bread. The facts presented in the investigation show that the baking quality of flour is modified considerably hy the mere mechanical processes to which it is subjected. Further studies are in progress a t the Food Research Institute a t Stanford to determine more fully the possibilitv of improvement of flour by its mechanical treatment.-Science SemMce
