Potentiometric Titration of Carboxyalkylated Poly Vinyl Alcohol with Mono-,Di-, and Trichloracetic Acids with Alkali Metals and Quaternary Ammonium Bases

Abstract

Potentiometric titrations of the obtained first carboxyalkylated products were carried out with LiOH, NaOH, KOH, NH₄0H, N(CH₃)₄OH and N(C₂H₅)₄OH in deionized water and with mixtures of LiOH and tetraethylammonium hydroxide of varying proportions. The experimental results were expressed in terms of the modified Henderson-Hasselbach equation pH ═ pK´a – n log [(1 – α/α)]. Appreciable shifts in the titration curves to lower pH values are observed, accompanied by increase in the values of calculated capacity of the polyelectrolyte, upon passing from N(C₂H₅)₄OH to N(CH₃)₄OH to NH₄OH to KOH to NaOH to LiOH. The values of pK´a (at α═ 0.5) and of n are found to increase with the size of counterion. The titration curves of the three polyelectrolytes with mixtures containing different proportions of LiOH and N(C₂H₅)4OH in deionized water, show that the calculated values of capacity and the position of the curves were intermediate between those obtained with the single cations. At the same value of α, the value of pH increased with the per cent of N(C₂H₅)₄OH relative to LiOH.