- #1
Baho Ilok
- 47
- 5
I want to prepare murexide indicator for Ca measurement using EDTA titrimetric method. I am following the procedure set by the American Public Health Association (APHA), however, I only have murexide diluted with K2SO4 (1:250). I want to know if I can use this as a substitute, and if yes, how.
The following is the procedure described by APHA:
Thanks!
The following is the procedure described by APHA:
Murexide (ammonium purpurate) indicator: This indicator changes from pink to purple at
the end point. Prepare by dissolving 150 mg dye in 100 g absolute ethylene glycol. Water
solutions of the dye are not stable for longer than 1 d. A ground mixture of dye powder and
sodium chloride (NaCl) provides a stable form of the indicator. Prepare by mixing 200 mg
murexide with 100 g solid NaCl and grinding the mixture to 40 to 50 mesh. Titrate immediately
after adding indicator because it is unstable under alkaline conditions. Facilitate end-point
recognition by preparing a color comparison blank containing 2.0 mL NaOH solution, 0.2 g solid
indicator mixture (or 1 to 2 drops if a solution is used), and sufficient standard EDTA titrant
(0.05 to 0.10 mL) to produce an unchanging color.
the end point. Prepare by dissolving 150 mg dye in 100 g absolute ethylene glycol. Water
solutions of the dye are not stable for longer than 1 d. A ground mixture of dye powder and
sodium chloride (NaCl) provides a stable form of the indicator. Prepare by mixing 200 mg
murexide with 100 g solid NaCl and grinding the mixture to 40 to 50 mesh. Titrate immediately
after adding indicator because it is unstable under alkaline conditions. Facilitate end-point
recognition by preparing a color comparison blank containing 2.0 mL NaOH solution, 0.2 g solid
indicator mixture (or 1 to 2 drops if a solution is used), and sufficient standard EDTA titrant
(0.05 to 0.10 mL) to produce an unchanging color.
Thanks!