Crystal violet cation

The crystal violet cation is the positively charged organic component of the crystal violet salt. Its molecular formula is ${\mathrm{C}}_{25}{\mathrm{H}}_{30}{\mathrm{N}}_3^{+}$, with net charge $+1$. The complete chloride salt additionally contains a chloride counterion; the isolated organic cation does not contain a chlorine atom.^[ref]

The cation contains three substituted aromatic rings and nitrogen-containing groups in a conjugated system. A drawn charged Lewis structure is a representation of that electronic system, rather than a claim that the molecular charge is a classical point permanently confined to the atom carrying the printed plus sign. Resonance distinguishes alternative electronic representations from different chemical substances.

An original mass check uses the ChEBI average masses $372.536\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$ for the cation and $407.989\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$ for the chloride formula unit. Their difference, $35.453\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$, is the chloride contribution under that atomic-mass convention. For $1.00\mathrm{mmol}$ of ideal anhydrous salt, the sample contains $1.00\mathrm{mmol}$ of dye cations and $1.00\mathrm{mmol}$ of chloride ions; the total sample mass is $407.989\mathrm{mg}$, not $372.536\mathrm{mg}$.

The organic cation accounts for about $372.536/407.989\simeq 91.31\%$ of that ideal salt's mass. Confusing the two molar masses therefore changes an amount calculation even when the desired number of dye ions is specified correctly. This stoichiometric distinction does not itself predict dye binding, solution speciation or the crystal violet biomass response.