Iodine content of oyster shells

A report is given of the investigation of the iodine content of oyster shells taken from the reefs found in the Gulf of Mexico. The pulverized shells as sold on the market contain 200 to 300 parts per billion of iodine. Water soluble and alcohol soluble iodides appear to be absent. The granulated undried shells contain 500 parts per billion of iodine. Apparently there is a loss of iodine due to the temperature at which the pulverized shells are dried.     

The blackening of photographic plates by positive ions of the alkali metals

A short review is included of previous work on the blackening of photographic plates by positive rays and rays of an analogous nature.The blackening of Eastman x-ray plates, by positive ions, has been measured as a function of the energy of the ions of Li, Na, K, Rb, and Cs. The energy of the ions required to produce a photographic density of D = 0.3 with a one minute exposure at a current density of 1.32 × 10^?8 amperes per cm.² ranged from 1420 electron-volts in the case of cæsium to 860 electron-volts in the case of Li⁷. Approximately 10⁵ ions are required at these energies to render developable one silver-halide grain. For a threshold density, D = 0.04, under the same conditions the energy ranged from approximately 920 to 460 electron-volts for Cs and Li⁷ respectively.Sensitivity comparisons were made between x-ray plates and process and schumannized process plates. Potassium ions with an energy as low as 137 electron-volts were recorded on Schumann plates, and it is possible that positive ions of one-third this energy can be recorded.