What is "thenard's blue"

Cobalt \Co"balt\ (k[=o]"b[o^]lt; 277, 74), n. [G. kobalt, prob. fr. kobold, kobel, goblin, MHG. kobolt; perh. akin to G. koben pigsty, hut, AS. cofa room, cofgodas household gods, Icel. kofi hut. If so, the ending -old stands for older -walt, -wald, being the same as -ald in E. herald and the word would mean ruler or governor in a house, house spirit, the metal being so called by miners, because it was poisonous and troublesome. Cf. Kobold, Cove, Goblin.]

1. (Chem.) A tough, lustrous, reddish white metal of the iron group, not easily fusible, and somewhat magnetic. Atomic weight 59.1. Symbol Co.

   Note: It occurs in nature in combination with arsenic, sulphur, and oxygen, and is obtained from its ores, smaltite, cobaltite, asbolite, etc. Its oxide colors glass or any flux, as borax, a fine blue, and is used in the manufacture of smalt. It is frequently associated with nickel, and both are characteristic ingredients of meteoric iron.

2. A commercial name of a crude arsenic used as fly poison.

   Cobalt bloom. Same as Erythrite.

   Cobalt blue, a dark blue pigment consisting of some salt of cobalt, as the phosphate, ignited with alumina; -- called also cobalt ultramarine, and Thenard's blue.

   Cobalt crust, earthy arseniate of cobalt.

   Cobalt glance. (Min.) See Cobaltite.

   Cobalt green, a pigment consisting essentially of the oxides of cobalt and zinc; -- called also Rinman's green.

   Cobalt yellow (Chem.), a yellow crystalline powder, regarded as a double nitrite of cobalt and potassium.