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Lab Reagents

Indicators, Chelating Agents & Test Papers

Acid-base and metal indicators, chelating ligands, crown ethers and test papers for titration end points, spot tests and complexation chemistry.
190 productsCOA + SDS with every lot
190 products · page 1 of 8
GridList
Acid red 249
CAS
6416-66-6
Formula
C29H20ClN3Na2O10S3
MW
748.1 g/mol
ZX-019505

Seeing an end point clearly, or binding a metal ion selectively, calls for the right indicator or ligand. This sub-category combines classical pH and redox indicators with metal-specific chelators and macrocycles. Examples include 2,2'-Bipyridyl (GR 99%+) for iron and copper determination, 2,6-Dichloroindophenol sodium salt for vitamin C titration, 1-Aza-18-crown-6 for cation binding studies, and DOTA derivatives used in chelator chemistry.

Indicator choice depends on the transition range and the colour contrast in your sample matrix. Chelating agents are chosen by stability constant, selectivity and solubility in the working solvent. Test papers suit quick field checks of pH, peroxide or specific ions where full instrumental analysis is not needed.

Solid indicators are supplied in small sealed bottles, while indicator solutions and papers carry an expiry date because they lose sensitivity over time. Each lot includes a COA and SDS. You can compare similar indicators side by side with the product compare tool before choosing.

Indicators, Chelating Agents & Test Papers: questions buyers ask

How do I choose an indicator for a titration?
Pick an indicator whose colour change range sits on the steep part of your titration curve. For a strong acid with a strong base most indicators work, but a weak acid needs one changing in the alkaline range, such as phenolphthalein. Coloured or turbid samples may need a mixed indicator or potentiometric detection.
Why do some indicator solutions stop working properly?
Many indicators oxidise, hydrolyse or absorb carbon dioxide once dissolved, which dulls the colour change or shifts it. Dichloroindophenol solutions, for example, lose strength within days. Store solutions as directed, check them against a known standard, and prepare fresh batches from the solid when the end point becomes unclear.
What separates a chelating agent from a simple indicator?
A chelating agent forms several bonds to one metal ion and holds it in a stable ring complex. Some chelators, such as EDTA, are used as titrants, while metal indicators are weaker chelators that change colour when the titrant takes their metal away. Crown ethers and DOTA derivatives are used for selective binding and labelling.

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