Dithizone

Structural formula
General
Surname	Dithizone
other names	3- (phenylamino) -1-phenylimino thiourea; 3-anilino-1-phenylimino-thiourea ( IUPAC ) ; 1,5-diphenylthiocarbazone;
Molecular formula	C 13 H 12 N 4 S
Brief description	blue-black crystalline powder
External identifiers / databases
EC number	200-454-1
ECHA InfoCard	100,000,413
PubChem	657262
Wikidata	Q416513
properties
Molar mass	256.33 g mol −1
Physical state	firmly
Melting point	165–168 ° C (decomposition)
solubility	almost insoluble in water; little in ethanol ; good in carbon tetrachloride and chloroform (with green color);
safety instructions
GHS labeling of hazardous substances Caution
H and P phrases	H: 315-319
	P: 305 + 351 + 338
Toxicological data	56 mg kg −1 ( LD 50 , mouse , iv ) ; > 500 mg kg −1 ( LD , rat , oral ) ;
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Dithizone is a bidentate chelate complexing agent that is used as a sensitive reagent in the (trace) analysis of heavy metals .

Dithizone was synthesized by Emil Fischer in 1878 and introduced by Hellmuth Fischer in 1925 as a heavy metal ion reagent.

presentation

Dithizone is formed by the reaction of phenylhydrazine with carbon disulfide . The diphenylthiocarbazide produced as an intermediate product dehydrates to dithizone when heated in a methanolic potassium hydroxide solution.

properties

Dithizone forms stable complexes with many heavy metal ions which are insoluble in water but dissolve in carbon tetrachloride. The solutions of these dithizonates have a characteristic color:


Metal ion X	colour	Structural formula
Fe , Mn , Cu , Co , Ni	violet
Bi , Sn , Cd , Zn , Pb	red
Ag , ed	yellow

On the basis of this coloration and the fixed stoichiometry, they can be determined qualitatively and quantitatively by colorimetric or photometric methods .

Based on the different solubilities of metal ions and metal ion complexes, dithizone is used in extractive titration. In this case, the aqueous solution of the analyte is titrated with a standard dithizone solution in chloroform.

Dithizion is temporarily diabetogenic , as this complexes zinc, which is required for the function of insulin .

use

The formation of dithizonate serves as a very sensitive method for the trace analysis of various heavy metal ions. The detection limit for lead is 4 · 10 ⁻⁸ g at a limit concentration of 1: 1 250,000. The one for zinc, when using extractive enrichment, is at a dilution of 1:50,000,000, ie. H. 1 µg in 50 ml of water. Individual proofs achieve proof of 10 to 100 ppm .

photos

Dithizone, pure substance
Dithizone, 0.025% solution / suspension in ethanol 96%
Dithizone in ethanol 96%, highly diluted

literature

A. Willmes: Text book chemical substances. 1st edition. Self-published, Thun / Frankfurt am Main 1990, ISBN 3-8171-1214-9 .
G. Iwantscheff: The dithizone and its application in micro- and trace analysis. Verlag Chemie, Weinheim / Bergstr. 1958, DNB 452279755 .

Individual evidence

↑ ^a ^b ^c ^d Entry on dithizone. In: Römpp Online . Georg Thieme Verlag, accessed on June 11, 2014.
↑ ^a ^b ^c Entry on 1,5-diphenyl-3-thiocarbazone in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
↑ ^a ^b Entry on dithizone in the ChemIDplus database of the United States National Library of Medicine (NLM) .

[Römpp-1] Entry on dithizone. In: Römpp Online . Georg Thieme Verlag, accessed on June 11, 2014.

[GESTIS-2] Entry on 1,5-diphenyl-3-thiocarbazone in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .

[ChemIDplus-3] Entry on dithizone in the ChemIDplus database of the United States National Library of Medicine (NLM) .