Colcothar

2 definitions found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Crocus \Cro"cus\ (kr[=o]"k[u^]s), n. [L., saffron, fr. Gr.
     kro`kos; cf. Heb. kark[=o]m, Ar. kurkum, Skr. ku[.n]kuma.]
     1. (Bot.) A genus of iridaceous plants, with pretty blossoms
        rising separately from the bulb or corm. {Crocus vernus}
        is one of the earliest of spring-blooming flowers; {Crocus
        sativus} produces the saffron, and blossoms in the autumn.


        [1913 Webster]
  
     2. (Chem.) A deep yellow powder; the oxide of some metal
        calcined to a red or deep yellow color; esp., the oxide of
        iron ({Crocus of Mars} or {colcothar}) thus produced from
        salts of iron, and used as a polishing powder.
        [1913 Webster]
  
     {Crocus of Venus} (Old Chem.), oxide of copper.
        [1913 Webster]

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Colcothar \Col"co*thar\ (k[o^]l"k[-o]*th[~e]r), n. [NL.
     colcothar vitrioli, fr. Ar. qolqo[.t]ar.] (Chem.)
     Polishing rouge; a reddish brown oxide of iron, used in
     polishing glass, and also as a pigment; -- called also
     {crocus Martis}.
     [1913 Webster]