[From photography to chrysotherapy: Fordos and Gelis salt]

In 1840, the French physicist Hippolyte Fizeau (1819-1896) proposed an auric chloride and sodium thiosulfate-based reagent to fix daguerreotypes. In 1843, two French pharmacists, Mathurin-Joseph Fordos (1816-1878) and Amedee Gelis (1815-1882), isolated its main ingredient in crystalline form and analysed it as a sodium aurothiosulfate. They recommended the use of an aqueous solution of this product to fix photographic negatives. In this way, the deterioration by sulfuration that negatives underwent with Fizeau's solution could be avoided. Fordos and Gelis salt came back in the news in 1924 when Prof. Holger Christian Mollgaard (1885-1973) from Copenhagen suggested it under the term Sanocrysine for use in tuberculosis. The enthusiasm which followed the initial trials led to its being adopted by many countries. In France, Danish Sanocrysine was commercialised by the Bordeaux pharmacist Jean Dedieu (1892-1968) while sodium aurothiosulfate was marketed as Thiocrysine by Usines du Rhone in Lyon, and as Chrysalbine by Maison Poulenc Freres in Paris. Chrysalbine became Crisalbine when the two companies merged to become Societe parisienne d'expansion chimique (Specia). However, inadequate results, the toxicity of auric derivatives and, especially from 1945 on, the advent of really effective tuberculostatic agents progressively led to the decline and abandonment of Fordos and Gelis salt in the treatment of tuberculosis.