Dithizone

Dpon heating diphenylthiocarbazide with methyl alcohohc potassium hydroxide dithizone (or diphenylthiocarbazone) (III) is produced ... 

Br , citrate, CE, 2,3-dimercaptopropanol, dithizone, EDTA, E, OH , NagP30io, SCN , tartrate, thiosulfate, thiourea, triethanolamine BE4, citrate, V,V-dihydroxyethylglycine, EDTA, E , polyphosphates, tartrate Citrate, CN , 2,3-dimercaptopropanol, dimercaptosuccinic acid, dithizone, EDTA, glycine, E, malonate, NH3, 1,10-phenanthroline, SCN , 820 , tartrate Citrate, V,V-dihydroxyethylglycine, EDTA, E , PO , reducing agents (ascorbic acid), tartrate, tiron... 

Using Figure 7.27, explain how an aqueous mixture of Cu +, Pb +, and Cd + can be separated by extraction with dithizone in CCI4. 

The determination of an analyte s concentration based on its absorption of ultraviolet or visible radiation is one of the most frequently encountered quantitative analytical methods. One reason for its popularity is that many organic and inorganic compounds have strong absorption bands in the UV/Vis region of the electromagnetic spectrum. In addition, analytes that do not absorb UV/Vis radiation, or that absorb such radiation only weakly, frequently can be chemically coupled to a species that does. For example, nonabsorbing solutions of Pb + can be reacted with dithizone to form the red Pb-dithizonate complex. An additional advantage to UV/Vis absorption is that in most cases it is relatively easy to adjust experimental and instrumental conditions so that Beer s law is obeyed. 

The measurment in twophase systems is discussed by the example of dithizonate of zinc, in pseudomonophase systems - by the example of zinc and cadmium complexes with l-(2-pyridylazo)-2-naphthol, lanthanoid ion complexes with l-(2-pyridylazo)-resorcin. 

Lead, tetraethyl. Dreschel-type 100 ml 0.1 M iodine 1.8-2.9 50-75 inn Dithizone Bismuth, thallium. 

The nature of the donor atoms in the chelating agent. Ligands which contain donor atoms of the soft-base type form their most stable complexes with the relatively small group of Class B metal ions (i.e. soft acids) and are thus more selective reagents. This is illustrated by the reagent diphenylthiocarbazone (dithizone) used for the solvent extraction of metal ions such as Pd2+, Ag+, Hg2+, Cu2+, Bi3+, Pb2+, and Zn2 +. ... 

The use of dithizone in combination with various organic bases for synergistic extraction has already been indicated (Section 6.4). 

Multi-element analyses involving solvent extraction and high performance liquid chromatography (HPLC) have also been described. The extracts, containing metal-chelate complexes with sulphur-containing reagents, such as dithizone and diethyldithiocarbamate, were used directly for determination of the metals by HPLC.14... 

Discussion. Diphenylthiocarbazone (dithizone) behaves in solution as a tautomeric mixture of (C) and (D) ... 

It functions as a monoprotic acid (pKa = 4.7) up to a pH of about 12 the acid proton is that of the thiol group in (C). Primary metal dithizonates are formed according to the reaction ... 

Some metals, notably copper, silver, gold, mercury, bismuth, and palladium, form a second complex (which we may term secondary dithizonates) at a higher pH range or with a deficiency of the reagent ... 

In general, the primary dithizonates are of greater analytical utility than the secondary dithizonates, which are less stable and less soluble in organic solvents. 

Dithizone is a violet-black solid which is insoluble in water, soluble in dilute ammonia solution, and also soluble in chloroform and in carbon tetrachloride to yield green solutions. It is an excellent reagent for the determination of small (microgram) quantities of many metals, and can be made selective for certain metals by resorting to one or more of the following devices. 

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