Ethylenediaminetetraacetic acid titrations first

Titrimetric methods based on the reaction of metal ions with a coordinating species (ligand) are more than 100 years old. If the ligand is attached to the metal by more than one functional group, it is said to be polyden-tate and the compound produced is called a chelate. The complexometric reagent that is easily the most widely used for the titration of unknown concentrations of metal ion is the hexadentate ligand ethylenediaminetetraacetic acid (EDTA), first recognized by Schwarzenbach in 1945. The structure of the molecule is... 

The utility of complexation titrations improved following the introduction by Schwarzenbach, in 1945, of aminocarboxylic acids as multidentate ligands capable of forming stable 1 1 complexes with metal ions. The most widely used of these new ligands was ethylenediaminetetraacetic acid, EDTA, which forms strong 1 1 complexes with many metal ions. The first use of EDTA as a titrant occurred in... 

Although the most sensitive line for cadmium in the arc or spark spectmm is at 228.8 nm, the line at 326.1 nm is more convenient to use for spectroscopic detection. The limit of detection at this wavelength amounts to 0.001% cadmium with ordinary techniques and 0.00001% using specialized methods. Determination in concentrations up to 10% is accomplished by solubilization of the sample followed by atomic absorption measurement. The range can be extended to still higher cadmium levels provided that a relative error of 0.5% is acceptable. Another quantitative analysis method is by titration at pH 10 with a standard solution of ethylenediaminetetraacetic acid (EDTA) and Eriochrome Black T indicator. Zinc interferes and therefore must first be removed. 

Years ago, the indicator used for the titration of calcium and magnesium was a soap solution. As long as calcium and magnesium were present, no soap suds would form. The solution was shaken continuously as the titrant was added, and the first appearance of soap suds was the endpoint. This was a difficult endpoint to reproduce. The discovery by Swartzenback that ethylenediaminetetraacetic acid (EOTA) would chelate with calcium and magnesium ended the soap... 

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