(9.) Bromine (Br).—­The bromide of magnesium and sodium exists in many salt springs, and it is from these that the bromine of commerce is obtained.  The metallic bromides give the same reactions on silver with the microcosmic bead and copper salt as the metallic chlorides.  The purplish color which, however, characterizes the chlorides, is more inclined to greenish with the bromides.  If the substance be placed in a flask or glass tube, and fused with bisulphate of potassa, over the spirit-lamp, sulphurous gas and bromine will be eliminated.  Bromine will be readily detected by its yellow color and its smell.  Bromine may be readily detected by passing a current of chlorine through the fluid, after which ether is added and the whole is agitated.  The ether rises to the top, carrying with it the bromine in solution; after being withdrawn, this ether is mixed with potassa, by which the bromide and bromate of potassa are formed.  The solution is evaporated to dryness, the residue is fused in a platinum vessel, the bromate is decomposed, while the bromide remains; this must be distilled with sulphuric acid and the binoxide of manganese.  A red or brown vapor will then appear, indicating the presence of bromine; this vapor will color starch paste—­which may be put in the receiver on purpose—­of a deep orange color.

If, to a solution containing a bromide, concentrated sulphuric or nitric acid be added, the bromine is liberated and colors the solution yellow or red.  The hypochlorites act in the same manner.  The bromine salts are coming into use extensively in photography, in consequence of their greater sensitiveness to the action of light than the chlorides alone.

(10.) Iodine (I).—­This element occurs in salt-springs, generally combined with sodium; it also exists in rock-salt; it has likewise been found in sea-water, also in a mineral from Mexico, in combination with silver, and in one from Silesia, in combination with zinc.  As sea-water contains iodine, we would consequently expect to find it existing in the sea-weeds, and it is generally from the ashes of these that it is obtained in commerce.

When the metallic iodides are fused with the microcosmic salt and copper, as previously indicated, they impart a green color to the flame.  This color cannot be mistaken for the color imparted to the flame by copper alone.  When the metallic iodides are fused in a glass tube, closed at one end, with the bisulphate of potassa, the vapor of iodine is liberated, and may be recognized by its characteristic color.  Those mineral waters containing iodine can be treated the same as for bromine, as previously indicated, while the violet-colored vapor of the iodine can be easily discerned.  The nitrate of silver is the best test for iodine, the yellow color of the iodide of silver being not easily mistaken, while its almost insolubility in ammonia will confirm its identity.  The chloride of silver, on the contrary, dissolves in ammonia with the greatest facility.