Malachite green metabolized into LMG. Only the cation MG is deeply colored, whereas the leuco and alcohol derivatives are not. This difference arises because only the cationic form has extended pi-delocalization, which allows the molecule to absorb visible light. The leuco form of malachite green was first prepared by Hermann Fischer in 1877 by condensing benzaldehyde and dimethylaniline in the molecular ratio 1:2 in the presence of sulfuric acid. Malachite green is traditionally used as a dye. Kilotonnes of MG and related triarylmethane dyes are produced annually for this purpose. MG is active against the oomycete "Saprolegnia", which infects fish eggs in
Italian submarine Malachite Crete, "Malachite" sighted a British cruiser escorted by a destroyer. She launched two torpedoes at the target, but they both missed her by the stern. From 3 to 14 July 1941 she patrolled north of Ras Azzaz. At 20:00 on July 3 "Malachite" sighted a large cruiser (possibly ) escorted by two destroyers, and immediately launched a torpedo. There was an explosion heard, but there is no reports of this attack in British post-war documents, although some believe an escort was hit. From September 25 to October 5 1941 she patrolled off Ras Aamer. From January 20 to 27, 1942