The Collaborative International Dictionary of English v.0.48:

Tropaeolin \Tro*pae"o*lin\, n. (Chem.)
   A name given to any one of a series of orange-red dyestuffs
   produced artificially from certain complex sulphonic acid
   derivatives of azo and diazo hydrocarbons of the aromatic
   series; -- so called because of the general resemblance to
   the shades of nasturtium (Tropaeolum).
   [1913 Webster]