Analytical Procedure
Quantitative chemical methods determine the acid or base content of a solution by adding a measured volume of a standard neutralising reagent. Executing a titrimetric neutralization allows dyehouse laboratories to check the residual alkali left on fabric after mercerizing or scouring. This analysis ensures that the textile has been sufficiently rinsed before proceeding to the dyeing stage.
Reaction Mechanism
The process involves adding a standardized acid solution, such as hydrochloric acid, to an alkaline extract of the fabric. An indicator dye or a pH electrode is used to detect the exact point where all the base is consumed. The volume of acid required for this change is then used to calculate the alkalinity of the specimen.
Dyeing Significance
Residual alkali on the fabric can cause premature dye fixation, leading to uneven shading and poor wash fastness. By ensuring complete neutralization, mills can prevent these defects and improve the reproducibility of the dyeing process. This testing is particularly important for sensitive shade groups like pastels and light greys.
Standard Method
Standard test methods describe the extraction and titration procedures for determining pH and alkalinity. Following these guidelines ensures consistent results across different laboratory operators and testing facilities.
