5-sulfosalicylic acid

Structural formula
General
Surname	5-sulfosalicylic acid
other names	2-Hydroxy-5-sulfobenzoic acid ( IUPAC )
Molecular formula	C 7 H 6 O 6 S (anhydrous) ; C 7 H 6 O 6 S · 2 H 2 O;
Brief description	white solid
External identifiers / databases
ECHA InfoCard	100.002.324
PubChem	7322
Wikidata	Q238569
properties
Molar mass	218.187 g mol −1 ; 254.22 g mol −1 (dihydrate);
Physical state	firmly
density	1.639 g cm −3 (20 ° C)
Melting point	105-109 ° C (dihydrate)
solubility	good in water (987 g l −1 at 20 ° C)
safety instructions
H and P phrases	H: 302-314
	P: 280-301 + 330 + 331-303 + 361 + 353-305 + 351 + 338-310
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

5-sulfosalicylic acid is a chemical compound from the group of sulfobenzoic acid derivatives . It is a white crystalline solid with a slightly pungent odor.

use

5-sulfosalicylic acid is used as an indicator in complexometry , preferably when determining iron (III) in an acidic medium ( pH ≈ 2.5). The determination of the iron is similar to that when using Tiron . The color changes from red to yellow.

application

Iron (III) forms a red chelate complex with 5-sulfosalicylic acid . 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 determination ends when the red color disappears, whereby the transition can sometimes be slow. The determination is relatively selective. Manganese, cobalt, nickel, copper and zinc do not interfere. Since the alkaline earth metals are titrated with EDTA in a weakly basic buffered medium, they do not interfere either.

If 5-sulfosalicylic acid and NH ₄ OH solution are added to iron (II) salts , a yellow complex is obtained which can be photometrically measured at 405 nm .

Complex of iron (II) and 5-sulfosalicylic acid

literature

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

Individual evidence

↑ ^a ^b ^c ^d ^e ^f Entry on 5-sulfosalicylic acid in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .

[GESTIS-1] ↑ ^a ^b ^c ^d ^e ^f Entry on 5-sulfosalicylic acid in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .