Xylenol orange

Xylenol orange
Names
	IUPAC name 3,3′-Bis[N,N-bis(carboxymethyl)aminomethyl]-o-cresolsulfonephthalein tetrasodium salt
Identifiers
CAS Number	1611-35-4 ; 3618-43-7 (tetrasodium salt) ;
3D model (JSmol)	Interactive image;
ChemSpider	65838 ;
ECHA InfoCard	100.015.049
EC Number	216-553-8;
PubChem CID	73041;
CompTox Dashboard (EPA)	DTXSID1061819 ;
	InChI InChI=1S/C31H32N2O13S/c1-17-7-21(9-19(29(17)42)11-32(13-25(34)35)14-26(36)37)31(23-5-3-4-6-24(23)47(44,45)46-31)22-8-18(2)30(43)20(10-22)12-33(15-27(38)39)16-28(40)41/h3-10,42-43H,11-16H2,1-2H3,(H,34,35)(H,36,37)(H,38,39)(H,40,41) Key: ORZHVTYKPFFVMG-UHFFFAOYSA-N ;
	SMILES O=C(O)CN(CC(=O)O)Cc1c(O)c(cc(c1)C3(OS(=O)(=O)c2ccccc23)c4cc(c(O)c(c4)CN(CC(=O)O)CC(=O)O)C)C;
Properties
Chemical formula	C31H32N2O13S
Molar mass	672.66 g·mol−1
Melting point	195 °C (383 °F; 468 K)
Solubility in water	200 mg/mL
Hazards
NFPA 704 (fire diamond)	2 1 2
Flash point	> 93 °C (199 °F; 366 K)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

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 titrand and become yellow once it reaches its endpoint. Historically, commercial preparations of it have been notoriously impure,^[1] sometimes consisting of as little as 20% xylenol orange, and containing large amounts of semi-xylenol orange and iminodiacetic acid. Purities as high as 90% are now available.

References

^ Gay, Craig; Collins, James; Gebicki, Janusz M. (1999), "Determination of Iron in Solutions with the Ferric–Xylenol Orange Complex", Analytical Biochemistry, 273 (2): 143–148, doi:10.1006/abio.1999.4207

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[1] Gay, Craig; Collins, James; Gebicki, Janusz M. (1999), "Determination of Iron in Solutions with the Ferric–Xylenol Orange Complex", Analytical Biochemistry, 273 (2): 143–148, doi:10.1006/abio.1999.4207

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