In the last case it becomes coated with a greyish-black layer of an oxide (dioxide (?)), at a red heat the layer consists of the trioxide (B1203), and is yellow or green in the case of pure bismuth, and violet or blue if impure; at a bright red heat it burns with a bluish flame to the trioxide.
Bismuth trifluoride, BiF3, a white powder, bismuth tribromide, BiBr 3, golden yellow crystals, bismuth iodide, Bi13, greyish-black crystals, are also known.
Glareola, which, though much less common, is known to have bred in England, has a considerable resemblance to the species last mentioned, but can be distinguished by the feathers of the axillary plume being white barred with greyish-black, while in the green sandpiper they are greyish-black barred with white.
Iodine is a greyish-black shining solid, possessing a metallic lustre and having somewhat the appearance of graphite.