Complexon

Nitrilotriacetic acid [tris(carboxymethyl)amine, NTA, Complexone 1] [139-13-9] M 191.1,... 

Purification as for phthalein complexone except that it was synthesised from thymolphthalein instead of cresolphthalein. 

Such reactions are not available for Bi but this can readily be determined by complexometric titration using ethylenediaminetetraacetic acid or similar complexones ... 

Macrocyclic Polyamines as Biological Cation and Anion Complexones — An Application to Calculi Dissolution... 

Other types of complexons for polyanions (e.g. polycarboxylates and phosphates) are linear ligands with polyguanidinium cations or polyammonium cations as functional groups 33). 

The method based on the precipitation of peroxometalate precursors enables to achieve additional purification during the process. Thus, the addition of complexonates, such as OEDP or EDTA, which form stable complexes with some polyvalent metals, prevents co-precipitation of the main impurities such as Fe, Co, Ni, Mn, Mg, etc., which in turn significantly increases the purity of the final product. Enhanced purification can also be achieved by recrystallization of the precursor. Particularly, the precipitation of ammonium peroxofluorometalates, such as ammonium peroxofluoroniobate ((NH4)3Nb04F4), as a primary precursor, leads to significant reduction of the titanium contamination. Ammonium peroxofluoroniobate, (NH4)3Nb04F4, is... 

Re-crystallization also leads to a significant reduction in the level of carbon and oxygen impurities however, the reduction of cationic impurities is usually not efficient. To prevent co-precipitation of complex fluorotantalates of polyvalent metals, some suitable complexonates are added to the solution. 

The nature of complexes, their stabilities and the chemical characteristics of complexones have been dealt with in some detail in Sections 2.21 to 2.27. This particular section is concerned with the way in which complexation reactions can be employed in titrimetry, especially for determining the proportions of individual cations in mixtures. 

The vast majority of complexation titrations are carried out using multidentate ligands such as EDTA or similar substances as the complexone. However, there are other more simple processes which also involve complexation using monodentate or bidentate ligands and which also serve to exemplify the nature of this type of titration. This is demonstrated in the determination outlined in Section 10.44. 

Thymolphthalein complexone (thymolphthalexone). This is thymolphthalein di(methyliminediacetic acid) it contains a stable lactone ring and reacts only in an alkaline medium. The indicator may be used for the titration of calcium the colour change is from blue to colourless (or a slight pink). Manganese and also nickel may be determined by adding an excess of standard EDTA solution,... 

Complexometric titration general discussion, 258, 309, 311, 322 see also EDTA Complexones 55 Computers 133... 

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