Tiron

Structural formula
General
Surname	Tiron
other names	Pyrocatechol-3,5-disulfonic acid disodium salt; 1,2-Dihydroxybenzene-3,5-disulfonic acid disodium salt ;
Molecular formula	C 6 H 4 Na 2 O 8 S 2
Brief description	white, odorless solid
External identifiers / databases
EC number	205-741-5
ECHA InfoCard	100.005.220
PubChem	9001
ChemSpider	8651
Wikidata	Q2436330
properties
Molar mass	314.20 g mol −1
Physical state	firmly
Melting point	300 ° C
solubility	very good in water (1350 g l −1 at 20 ° C)
safety instructions
GHS labeling of hazardous substances Caution
H and P phrases	H: 315-319
	P: 302 + 352-305 + 351 + 338
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Tiron (also pyrocatechol-3,5-disulfonic acid disodium salt) serves as an indicator in complexometry , preferably for the determination of iron (III) in an acidic medium ( pH ≈ 2.5). The determination of iron is similar to that when using 5-sulfosalicylic acid . The color changes from blue-green to yellow.

application

Iron (III) forms a blue-green chelate complex with tiron . In order to enable a complete determination of the iron, any iron (II) present must be oxidized to iron (III). When titrating with EDTA , the iron is displaced from the chelate complex. The color change to yellow can sometimes be slow, so that you have to add some indicator solution at the end of the titration. The determination is relatively selective. Since the alkaline earth metals are titrated with EDTA in a weakly basic buffered medium, they do not interfere.

Individual evidence

↑ ^a ^b ^c ^d ^e Tiron data sheet (PDF) from Merck , accessed on March 18, 2011.

literature

Complexometric determinations with Titriplex (edited by E. Merck , Darmstadt)

[merck-1] Tiron data sheet (PDF) from Merck , accessed on March 18, 2011.