Temperature Dependent Drift in Textile Extract Ph Testing Laboratories
Controlling textile extract measurement temperature within 20 °C ± 1 °C prevents temperature-induced pH drift and false ISO 3071 compliance rejections.
Ion Activity
Chemical Mobility
Thermodynamic behavior of dissolved electrolytes in aqueous treatment baths is determined by their effective concentration rather than their raw molar value. The effective concentration is known as the ion activity, which accounts for the electrostatic interactions between charged particles in a solution. Such behavior governs the rate of chemical reactions during textile wet processing.
Dyeing Reaction
In reactive dyeing of cotton, the addition of salt increases the ion activity of the sodium ions, which screens the negative charge of the cellulose. This screening allows the anionic dye molecules to approach the fiber and form covalent bonds. If the activity of these ions is too low, the dye remains in the bath.
Activity Coefficient
Laboratory calculation of this value utilizes the product of the molar concentration and the activity coefficient of the specific ion. This coefficient decreases as the total ionic strength of the solution rises due to the shielding effect of the surrounding ions. In highly concentrated dye baths, this deviation becomes substantial and must be accounted for in process simulations.
This measurement prevents the miscalculation of chemical additions.
Practical Application
Precision dosing systems adjust the salt concentration to maintain consistent ion activity throughout the cycle. This control ensures uniform exhaustion of the dye.