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
Malachite for decorative purposes, such as in the Malachite Room in the Hermitage Museum, which features a huge malachite vase, and the Malachite Room in Castillo de Chapultepec in Mexico City. "The Tazza", a large malachite vase, one of the largest pieces of malachite in North America and a gift from Tsar Nicholas II, stands as the focal point in the centre of the room of Linda Hall Library. Malachite has also been used on the base of the FIFA World Cup Trophy. A 17th-century Spanish superstition held that having a child wear a lozenge of malachite would help them sleep,