XYLENOL ORANGE TETRASODIUM SALT ACS GRADE excellent quality manufacturer, exporter and supplier. Xylenol orange is an organic reagent, most commonly used as a tetrasodium salt as an indicator for metal titrations. When used for metal titrations, it will appear red in the titrant and become yellow once it reaches its endpoint.


Xylenol Orange Tetrasodium Salt ACS Grade supplier in Mumbai, Kandla, Kolkata, Chennai, Visakhapatnam – INDIA

Technical Specifications:
C.A.S. No. 3618-43-7
M.F. C31H28N2SO13Na4
M.W. 760.59gm/mole



Solubility 0.1% (Dist. water) Clear solution
Absorption maximum (0.1N NaOH) ?max 575-580nm
Absorptivity (A1%/1cm in 0.1N NaOH, at ?max) >620
Loss on drying (110°C) <8%
Suitability for Zinc titration Passes test

The particular pH used to buffer the titration solution was also chosen because of the metal ion indicator used to signal the end point in the titration. A metal ion indicator is a substance that changes color when it binds to metal ions in solution. Metal ion indicators tend to be polyprotic complexing agents. Xylenol orange  is used for the cobalt titration. This indicator is red when it forms a complex with metal ions such as Co2+. However, the color of the unbound (free) indicator depends on pH and which protonated form is predominantly present. Above pH = 6.7, free xylenol orange is violet and the color change from red to violet is not sharp. However, below pH = 6.7 the free indicator color is yellow and the change from red to yellow is
much easier to see.

A small amount of xylenol orange is added initially to the cobalt solution and it forms a complex with some of the Co2+. As EDTA is added to this solution, the EDTA complexes the free Co2+. Just before the equivalence point, the free Co2+ is used up and the EDTA starts to remove cobalt ion from the indicator. As the xylenol orange loses the metal ion, its color changes. Obviously, the indicator must not bind the metal ion as strongly as the complexing agent (EDTA) used for the titration.

Note: This article uses material from the