In engineering uses this metal serves as a hardening constituent for anti-friction alloys. It also causes these alloys to expand after they are poured into place, making them fill completely, when cold, the space intended for them. It is grayish white, extremely brittle, has a peculiar odor, and melts at about 850° F.

Its usual commercial form, the regulus of antimony, is a somewhat impure metal extracted from its compound with sulphur.