Fast red TR salt hemi (zinc chloride) is a diazonium dye with red color.
[1]. Newton P, et al. Fake artesunate in southeast Asia. Lancet. 2001 Jun 16;357(9272):1948-50.
[1]. Newton P, et al. Fake artesunate in southeast Asia. Lancet. 2001 Jun 16;357(9272):1948-50.