Metal phthalein

Structural formula
General
Surname	Metal phthalein
other names	Phthalein Purple; 5 ', 5' '- bis [ N , N -bis (carboxymethyl) aminomethyl] -cresolphthalein; Xylenolphthaleinbis (iminodiacetic acid); o -Cresolphthalexone; o -Cresolphthalein complexone;
Molecular formula	C 32 H 32 N 2 O 18
Brief description	beige, odorless, crystalline powder
External identifiers / databases
EC number	219-318-8
ECHA InfoCard	100.017.563
PubChem	75485
ChemSpider	68014
Wikidata	Q907634
properties
Molar mass	636.62 g mol −1
Physical state	firmly
Melting point	186 ° C
solubility	almost insoluble in water
safety instructions
GHS labeling of hazardous substances	no GHS pictograms
	no GHS pictograms
H and P phrases	H: no H-phrases
	P: no P-phrases
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Metal phthalein is a triphenylmethane dye and belongs to the group of phthaleins. The analogous sulfonphthalein is xylenol orange . It is used as an indicator in complexometry .

Chemical properties

Metal phthalein contains a lactone ring , four carboxy , two amino and two hydroxyl groups , each of which can be protonated or deprotonated. Furthermore, the lactone ring can also be cleaved in a strongly acidic or basic environment. At pH ≈ 12–13, metal phthalein is pink in color. In this form, metal phthalein now forms a weak purple-colored complex with some divalent metal ions , which is destroyed again by adding a stronger complexing agent such as EDTA .

use

In addition to eriochrome black T , metal phthalein is used as an indicator in complexometry for the determination of Ba ²⁺ , Ca ²⁺ , Cd ²⁺ , Mg ²⁺ and Sr ²⁺ .

Individual evidence

↑ ^a ^b ^c ^d ^e data sheet metal phthalein (PDF) from Merck , accessed on December 25, 2019.
↑ M. Hübel, Ciba Geigy et al .: Laborpraxis. Volume 4, 5th edition, Birkhäuser-Verlag, Basel 1996, p. 123 ( limited preview in the Google book search)
↑ Entry on metal phthalein. In: Römpp Online . Georg Thieme Verlag, accessed on September 25, 2017.
↑ aprentas (ed.): Laborpraxis . 6th edition. tape 4 : Analytical methods . Springer-Verlag, 2017, ISBN 978-3-0348-0972-6 , pp. 29 ( limited preview in Google Book search).

[Merck-1] ↑ ^a ^b ^c ^d ^e data sheet metal phthalein (PDF) from Merck , accessed on December 25, 2019.

[Googlebook-2] M. Hübel, Ciba Geigy et al .: Laborpraxis. Volume 4, 5th edition, Birkhäuser-Verlag, Basel 1996, p. 123 ( limited preview in the Google book search)

[3] Entry on metal phthalein. In: Römpp Online . Georg Thieme Verlag, accessed on September 25, 2017.

[4] rentas (ed.): Laborpraxis . 6th edition. tape 4 : Analytical methods . Springer-Verlag, 2017, ISBN 978-3-0348-0972-6 , pp. 29 ( limited preview in Google Book search).