IN the course of work on the transmission of acoustic waves through aqueous solutions, we have noticed that solid substances in process of solution become extremely efficient absorbers of acoustic energy. In a typical experiment in which transmission was taking place at 400 kc./s. between transducers 1 ft. apart, the addition of 1 per cent by weight of common salt to the water produced attenuation of the order of 40 db., which was maintained until solution was complete. It was found that similar effects could be produced with all soluble solids, but not with liquids; and that although the amount of attenuation varied, it was in all cases high compared with that produced by insoluble substances.