The properties of chlorotrihydroxydihydrophenazine were thoroughly investigated. Oxidations with sodium perborate or hydrogen peroxide in glacial acetic acid gave chloro-trihydroxyphenazine-5,10-dioxide. Methylation gave a monomethyl derivative and acetylation yielded mono-, di-, and tri-acetyl derivatives. Benzoylation gave a tetrabenzoyl compound. Bromination gave a monobromo derivative. Nitrosation produced a mononitroso and nitration a mononitro compound. Degradation by zinc dust distillation and thermal decomposition yielded phenazine. Molecular weight and absorption spectra determinations supported the chemical evidence that the compound was 1-chloro-2(or 3),6,8-trihydroxydihydrophenazine. 1,4,9-Trichloro-2(or 3),6,8-trihydroxydihydrophenazine, 1,4,9-trichloro-2(or 3, or 8),6-dihy-droxydihydrophenazine, and 1-bromo-2(or 3),6,8-trihydroxydihydrophenazine were similarly identified.