The dissolution of some superficial sediments was studied experimentally to determine the sediment's influence on groundwater composition and also to check the previous findings based on analyses of the sediment and of the natural pore water from a site at Dunsforth, 21 km north-west of York. In the experiments Ca was dissolved from carbonates, Mg from dolomite and clay minerals, K and probably Na also from clay minerals and possibly feldspars. Higher concentrations of Ca, Mg and K were dissolved from unweathered sediments than from weathered, whereas the concentration of Na remained relatively constant. These conclusions are in agreement with those based on a study of the natural system and thus some of the reactions can be reproduced in the laboratory. Equilibrium was achieved relatively rapidly in the experiments. It is therefore claimed that relatively simple experimental work can provide meaningful information in studies of groundwater chemistry.