Also cæ-. [f. L. cærule-us blue + -IN.] † a. An intensely blue substance obtained from indigo. b. A deep blue substance contained in many essential oils, also called azulene.
1810. Henry, Elem. Chem. (1840), II. 281. Cerulin appeared to consist of 1 atom of indigo + 4 atoms of water.
1838. T. Thomson, Chem. Org. Bodies, 200. He gave the name of cerulin, from its blue colour, to the soluble indigo contained in it, and that of ceruleo-sulphates to the salts.
1872. Watts, Dict. Chem., IV. 185. An oily compound of a very deep blue colour called cærulein.
1880. Syd. Soc. Lex., Cærulein, same as Azulene.
