Gold Bromide (HAuBr4)
The most reliable test for 4-FMC is the gold bromide test. The substance forms long red serrated blades that start as short orange blades. The blades overtake the drop over time and can be readily identified. The blades are a deep orange to red under crossed polars.
The blades can be easily maneuvered onto IR substrates to obtain information-rich spectra.