Anthracine blue composition

Question

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.

Answer 1

Springmühl indeed reported Anthracene Blue (orig. "Anthracenblau" (German)) from an intermediate with brutto-formula $\ce{C14H7O3}$. It seems like this method only worked well at a lab scale.

According to Springmühl's Lexicon der Farbwaaren und Chemikalienkunde [1, p. 111-112], Anthracene Blue is obtained as a byproduct of oxidation of anthracene to anthraquinone by fuming nitric acid. When gas (hydrogen in original text) evolution stops, resulting solution is neutralized with potash and heated under pressure in a sealed glass tube for 8 hours. Dark-green precipitation is then filtered off, and deep-blue solution containing Anthracene Blue is then treated with sodium chloride to precipitate the product in a form of blue water-soluble powder. But, treated with tannic acid, Anthracene Blue forms dark-blue precipitate and cannot be dissolved neither in water, nor in alcohol; but slightly soluble in acidified solutions.

Original German text:

Springmühl, der Entdecker des Anthracenblau, stellte dasselbe zuerst dar, indem er eine Verbindung von der Zusammensetzung $\ce{C14H7O3}$, welche er bei der Oxydation des Anthracens neben Anthrachinon erhielt, mit rauchender Salpetersäure behandelte und auf das erhaltene Product Wasserstoff in statu nascendi einwirken liess, die resultirende Lösung mit Kali versetzte und unter Druck erhitzte. Es bildete sich eine tiefblaue Färbung in der zugeschmolzenen Glasröhre und nach 8stündiger Erhitzung fand sich ein dunkelgrüner fast schwarzer Niederschlag in derselben, während die Lösung tiefblau gefärbt war und das Anthrancenblau enthielt, es liess der Farbstoff aus filtrirter Lösung sich mit Chlornatrium niederschlagen und mit Gerbsäure konnte der in Wasser wieder gelöste Farbstoff völlig als dunkelblaues Pulver gefällt werden, welches weder in Alkohol noch Wasser, hingegen leicht in Säuren sich löste.

Later synthetic process was changed to adapt it for industrial production. Beilstein catalogue from 1925 lists Anthracenblau-WR as 1,2,4,5,6,8-hexahydroxy-9,10-anthraquinone $\ce{C14H8O8}$ [2, p. 569], which can be obtained from 3-hydroxybenzoic acid with concentrated $\ce{H2SO4}$ in the presence of $\ce{H3BO3}$ at $\pu{260 .. 280^\circ C}$. The product is then poured into water and boiled. Alternatively, 3,5-dihydroxybenzoic acid can be used. There are also plenty other synthetic techniques slightly deviated from the mentioned above.

These days Anthracenblau is also known as commercially available dye Anthracene Blue (S)WR.

Reference

1. Springmühl, F. Lexicon der Farbwaaren und Chemikalienkunde: practishes Handbuch für Kenntiniss und Prüfung aller in der Industrie und im Gewerbebetrieb verwendeten Farbstoffe und Chemikalien; Leipzig: Gustav Weigel, 1877. (in German, Archive.org)
2. Beilsteins Handbuch der Organischen Chemie, 4th Ed.; Prager, B., Jacobson, P., Schmidt, P., Stern, D., Eds.; Springer: Berlin, 1925; Vol. 8. (in German, Archive.org)