because its value shows whether the sand and the resin can work
together. The experimental procedure employed in this study foresees the addition of
50 ml of distilled water and 50 ml of 0.1 N hydrochloric acid to a sample of a weight
equal to 50 g. After 15 min of vigorous stirring, the sample is washed twice with 100
ml of distilled water, and the liquid phases are titrated, using a Orion 420 pH-meter,
with a 0.1 N sodium hydroxide solution till a pH value equal to 5 is reached