# Methylene blue used as funguscide in cichlid reproduction - concentration measurement?

I have an aqueous solution of methylene blue. How do I determine the concentration of this solution, so I can duplicate it?

• Do you have access to a UV-VIS spectrometer? Feb 13 '15 at 20:04
• As @KlausWarzecha said, what kind of equipment/instruments do you have access to? Feb 13 '15 at 20:38

Measure the absorption at $\lambda = 664\, \mathrm{nm}$, use the molar extiction coefficient of $95000\, \mathrm{dm^{3}\cdot mol^{-1}\cdot cm^{-1}}$ (Reference) and calculate the concentration using the Lambert-Beer equation.