Metallic iodides and bromides behave upon charcoal in a similar manner to the chlorides. Those principally deserving of mention are the bromides and iodides of potassium and sodium. These fuse upon charcoal, are absorbed into its pores, and volatilize in the form of white fumes, which are deposited upon the charcoal at some distance from the assay. When the saline films so formed are submitted to the reducing flame, they disappear, coloring the flame in the same manner as the corresponding chlorides. 4. EXAMINATIONS IN THE PLATINUM FORCEPS. Before the student attempts to make an examination in the platinum forceps or tongs, he should first ascertain whether or not it will act upon the platinum. If the substance to be examined shall act chemically upon the platinum, then it should be examined on the charcoal, and the color of the flame ascertained as rigidly as possible. The following list of substances produce the color attached to them. A. VIOLET. Potash, and all its compounds, with the exception of the phosphate and the borate, tinge the color of the flame violet. B. BLUE. Chloride of copper, Intense blue. Lead, Pale clear blue. Bromide of copper, Bluish green. Antimony, Bluish green. Selenium, Blue. Arsenic, English green. C. GREEN. Ammonia, Dark green. Boracic acid, Dark green. Copper, Dark green. Tellurium, Dark green. Zinc, Light green. Baryta Apple green. Phosphoric acid, Pale green. Molybdic acid, Apple green. Telluric acid, Light green. D. YELLOW. Soda, Intense yellow. Water, Feeble yellow. E. RED. Strontia, Intense crimson. Lithia, Purplish red. Potash, Violet red. Lime, Purplish red. The student may often be deceived in regard to the colors: for instance, if a small splinter of almost any mineral be held at the point of the flame of oxidation, it will impart a very slight yellow to the flame. This is caused, doubtless, by the water contained in the mineral. If the piece of platinum wire is used, and it should be wet with the saliva, as is frequently done by the student, then the small quantity of soda existing in that fluid will color the flame of a light yellow hue. A. THE VIOLET COLOR.