Patent US387876: Process of preparing aluminium bronze and other alloys. Angemeldet am 27. Dezember 1887, veröffentlicht am 14. August 1888, Erfinder: Paul Héroult (Zitat: „Again, the flux may evolve gases, which will settle on the carbon anode and tend to polarize it and by preventing free access of the oxygen to the carbon increase the resistance and the cost of production. For instance, I have used cryolite (which can be fused by external heat without a flux) as an electrolyte, and also as a flux in connection with alumina, but have found it objectionable, because it evolves fluorine, which does not, like the oxygen evolved from alumina, combine with the carbon anode and pass off, but settles upon it with the effect above mentioned.“).
