We investigated charge changing collisions using the experimental technique of automatic track measurement for etched tracks in CR39. For beams of 40 Ar and 56 Fe altogether more than 33600 interactions of beam nuclei and about 15600 interactions of fragments produced in nuclear collisions were analyzed. Besides interactions with the light target nuclei H, C and O of the plastic detectors also interactions with silver target nuclei were studied. For this purpose we stacked silver foils between the plastic detector foils. Cross sections for the production of fragments with Z⩾8 from nuclei with 9⩽Z⩽26 in charge changing nuclear collisions were determined.