Automated Potentiometric Titration Protocols for High Salinity Reactive Dyeing Baths
Automated potentiometric titration using double-junction glass electrodes resolves active hydroxide and carbonate alkalinity in high-salinity reactive dye baths.
Total Active Alkalinity
Alkaline Concentration
Chemical bath strength in wet processing defines the total concentration of basic compounds available to react with natural fibers. Measuring total active alkalinity quantifies the combined molarity of sodium hydroxide and sodium carbonate in cotton prep liquors.
Titrimetric Determination
Two-stage acidimetric titration using phenolphthalein and methyl orange indicators separates active hydroxide from carbonate contributions. Standardized hydrochloric acid neutralizes free hydroxyl ions during the first endpoint transition before converting carbonates to bicarbonates and carbon dioxide gas. Automated potentiometric titrators record pH inflection points continuously, eliminating subjective visual color judgment.
Results express effective bath strength in grams per liter of equivalent sodium hydroxide.
Effective Threshold
Process control limits dictate target alkalinity based on fabric weight, fiber impurities, and processing speed. Insufficient alkaline strength causes incomplete wax saponification and uneven seed coat removal during preparation. The measurement metric does not apply to neutral or acidic dye liquors where basic reagents are absent.
Heavy contamination by dissolved size or organic soil buffers acid additions, requiring sample filtration before testing.
Bath Maintenance
Automated chemical replenishment based on titration data maintains uniform swelling and scouring efficiency across continuous production runs. Stable bath composition ensures consistent dye affinity and absorbency in finished fabrics.