The Acid Elements
24. Borates.—If the substance be finely powdered, moistened with glycerine, and then placed on a platinum wire in the Bunsen flame, it imparts a brilliant green color.
If turmeric paper be dipped into a solution of a borate, and then be dried at 100° C., it is turned to a peculiar red color. These two reactions are extremely delicate.
25. Bromides.—Bromides treated with microcosmic salt and oxide of copper on platinum wire impart to the flame a greenish-blue color, the edges being decidedly green.
26. Chlorides.—Chlorides are treated in the same way as bromides. The color imparted to the flame is azure-blue.
To discriminate between bromides and chlorides more clearly, the substance is mixed with anhydrous potassium bisulphate and fused in an ignition tube.
Bromine and sulphur dioxide are evolved (if the substance be a bromide), the tube being filled with a yellow gas possessing the characteristic odor of bromine.
27. Fluorides.—A small portion of the substance in a finely powdered condition is placed in one of the ignition tubes, a strip of moist Brazil-wood paper is introduced into the open end, and heat is applied. Hydrofluoric acid is evolved, and the red color of the paper is changed into a straw-yellow.
Mica, containing only 0.75% of fluorine, shows the reaction clearly.
28. Iodides.—Iodides are treated, as the bromides and chlorides, in a bead of microcosmic salt with oxide of copper. The flame is colored green.