Iodine green
Description
An important aniline-based green dye patented in 1865 by James Wanklyn, an English chemist. Iodine green was discovered as an accidental but highly valuable byproduct during the manufacture of Hofmann's violet. Wanklyn and Paraf developed the synthesis by heating Hofmann's violet (triethylrosaniline) in sealed tubes with methyl iodide. The resulting reaction yielded the vibrant green compound alongside other methylated derivatives.
Chemically, iodine green is the trimethyliodide of trimethylrosaniline. It is structurally and functionally very close to other synthetic green dyes like Methyl green and Ethyl green but features an additional methyl group. While iodine green was initially used for dyeing wool, silk and cotton textiles, it has since been replaced by more durable dyes. Iodine green is still iused for microscopic staining of biological tissues.
Physical and Chemical Properties
- Soluble in water and ethanol.
- Insoluble in benzene and ether.
- Composition = C20H16(CH3)3N3(CH3I)2
- Decomposition occurs at 100 C
- Poor light and wash fastness.
Resources and Citations
- W.M.Gardner (ed.). The British Coal-Tar-Industry. Its Origin, Development and Decline. J.B Lippincott Co. Philadelphia, 1915. Link
- M.J. Plater, A. Raab, H. Hartmann 'Liquid Chromatography-Mass Spectrometry analysis is some early green dyes' Journal of Chemical Research, Sept. 2024.
- E. Hagan, I. Castro-Soto, M. Breault, et al. The lightfastness of early synthetic organic dyes. Herit Sci 10, 50 (2022).