Meaning
Chemical solutions designated for the anodic compartment of a titration cell provide the necessary environment for moisture detection. These anolyte reagents contain sulfur dioxide and an organic base along with an iodide salt dissolved in a suitable solvent. When a polymer sample is processed through a moisture analyzer, the reagent enables the chemical conversion of water into a measurable electrical charge.
High purity is required.
Chemical Composition
Ingredients within the solution are balanced to maintain a specific pH level and electrical conductivity. Most anolyte reagents utilize a mixture of imidazole and sulfur dioxide to facilitate the reaction between the water and the iodine. The choice of solvent, often a combination of methanol and chloroform, determines how well the reagent dissolves different types of polymer additives or lubricants.
Oxidation Reaction
Electrochemical activity at the anode converts iodide into free iodine which then reacts with the water molecules. This part of the process is governed by the stoichiometry of the sulfur dioxide reaction.
Solution Longevity
Exhaustion of the chemicals occurs as the sulfur dioxide is consumed or the solvent becomes saturated with sample debris. Monitoring the total water capacity helps a laboratory decide when to replace the fluid to maintain accuracy.
