11.- The Action o,f Water o n Bismwthous Iodide a Lecture Experiment. By M. M. PATTISON MUIR. THE action of water on bismuthous iodide affords a reaction well adapted for illustrating the influence of (u) time ; ( 6 ) temperature ; (c) mass on a chemical change. The experiment may be conducted in two ways the second of which is I think perhaps the best the meaning o€ the expressions " direct " and " reverse " action may also be well illustrated by this modification of the experiment. A quantity of aqueous hydriodic acid-about 1 part strong acid to 100 parts water-is divided into two equal parts ; one is heated to boiling, the other remains cold a small quantity of the cold solution is diluted with about three times its own bulk of water ; a little of this is again diluted with about three or four times its own bulk of water.The four liquids are placed in beakers standing on whike surfaces with white backgrounds and a few grains of solid bismuthous oxide are shakeu into each. I n the cold comparatively concentrated liquid, brown BiI is produced ; in the hot liquid red BiOI ; in the cold and moderately dilute BiOI ; and in the most dilut,e there is little or no action. The brown BiI slowly changes on standing to red BiOI. The experiment may be conducted more easily and with more striking effect by pouring R little of a solution of BiT in concentrated hydriodic acid into three beakers standing on white surfaces and with white backgrounds and containing (1) a little cold water (about 100 o.c.); (2) the same quantity of water at about 90-100"; (3) a large quantity (about 500 c.c.) of cold water. Brown BiI is precipi-tated in (1) ; red crystalline BiOI in (2) ; and red BiOI but in smaller quantity in (3). Here again the brown BiI is slowly changed to red BiOI on standing by pouring a little strong hydriodic acid inho this beaker after this change is nearly complete the reverse change-with reproduction of brown Bi13-is rendered very apparent