In 1873 a German chemist named Springmühl announced a derivative of alizarin which acted as a blue dye and he sold this dye for a high price. The dye was sometimes called "anthracine blue" and Springmuhl kept the process for producing it a secret.
Has the composition of this dye ever been revealed?
From Chemical News, April 25, 1873:
Anthracene Blue.— A few years since aniline was the great source of new and beautiful colours. Now that every possible shade of colour, surpassing in number and beauty the hues of the rainbow, have been produced from aniline, the chemist has taken up the study of anthracene and alizarine, also coal-tar products. While preparing artificial alizarine from anthracene, Springmühl has obtained a by-product, from which he has made a beautiful blue colour, superior in some respects to any of the aniline blues. The process by which it was prepared he keeps a secret. Dried in vacuo, it is a blue powder with a few little crystals. In this it differs from the aniline dyes, which are one colour when dry, another when in solution. When pure hot water is poured over anthracene blue it mostly dissolves, but leaves a little insoluble residue. The addition of an alkali destroys its colour, which is restored, however, by an acid. The strongest mineral acids are unable to destroy its colour, but rather heightens its tone. Unlike aniline dyes, it is insoluble in alcohol and ether. Experiments show that it withstands the action of light better than aniline blue. Unfortunately, it is at present very expensive, for Springmühl obtained but 2'5 grains of anthracene blue from 25,000 grains of anthracene, which makes it cost about 3000 dols, per pound at present. A cheaper method of making it is certainly desirable.—American Artizan.