Metalloid for carbon in steel casting. Of the non-metallic elements less often recognised as metalloids, selenium—in the form of ferroselenium (50–58% selenium)—is used to improve the machinability of stainless steels. All six of the elements commonly recognised as metalloids have toxic, dietary or medicinal properties. Arsenic and antimony compounds are especially toxic; boron, silicon, and possibly arsenic, are essential trace elements. Boron, silicon, arsenic, and antimony have medical applications, and germanium and tellurium are thought to have potential. Boron is used in insecticides and herbicides. It is an essential trace element. As boric acid, it has antiseptic, antifungal, and antiviral properties.
Germanium disulfide is restricted to fumaroles of some burning coal-mining waste heaps. Germanium disulfide Germanium disulfide or Germanium(IV) sulfide is the inorganic compound with the formula GeS. It is a white high-melting crystalline solid. The compound is a 3-dimensional polymer, in contrast to silicon disulfide, which is a one-dimensional polymer. The Ge-S distance is 2.19 Å. Germanium disulfide was the first germanium compound found by Clemens Winkler, during the analysis of argyrodite. The fact that germanium sulfide does not dissolve in aqueous acid made it possible for Winkler to isolate the new element. Germanium disulfide is created by reacting hydrogen sulfide with