Determination of total sulphonate

This procedure measures the total matter soluble in propan-2-ol and its apparent mean molecular weight. It is assumed that the product is the sodium salt if it is the free mixed acids, it must first be neutralised to phenolphthalein with sodium hydroxide. The results give no information about the composition of the propan-2-ol solubles, but the method could be useful for quality control of raw materials. 

Dry a 5 g sample in a 250 ml beaker, add 100 ml dry propan-2-ol, cover with a watch-glass and boil gently on a steam bath for 30 min. 

Cool and filter into a tared beaker. Wash the filter with pro-pan-2-ol, collecting the washings in the same beaker as the filtrate. 

Evaporate to dryness on a steam bath (caution flammable vapour), dry at 105°C for 1 h, cool and weigh. Calculate the percentage of propan-2-ol-soluble matter. 

Pass the solution through a column containing 40 ml of a strongly acidic cation-exchange resin with 4% cross-linking, in the free acid form, in 80% methanol. 

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