A procedure for isolating the high molecular-weight fraction of a commercial lignosulfonate sample by size exclusion chromatography is described together with the desalting process for that fraction.
Conductance of aqueous solutions of the lithium, sodium, and potassium salts of the original lignosulfonate, the isolated lignosulfonate, and a standard poly(styrene sulfonate) sample were then measured at 25°C. Experiments covered a large concentration range between 0.2 and about 100 eq m−3.
The resulting equivalent conductance, for all cases, increased sharply when the concentration decreased to a very dilute limit after which it decreased steeply. Those results showing relatively high conductances for lignosulfonate allowed a comparison of its electrolyte behavior with that of poly(styrene sulfonate) on the basis of the complex chemical composition and structure of lignins.