Abstract: A process and system for recovering the materials from an aqueous solution is disclosed. Dissolved materials in the aqueous solution are solidified as the aqueous solution is caused to be changed from liquid to vapor state, and the solidified materials along with suspended materials, if any, are collected. The aqueous solution is caused to be changed from liquid to vapor state at a filter which passes the vapor but blocks passage of liquid, and the filter has a vacuum at the side opposite to that of the aqueous solution so that the vapor is withdrawn through the filter and the solid materials collected on the filter. The system includes a thin film filter that is releasably clamped against a container so that one side of the filter contacts aqueous solution such as water in the container with a vacuum pumping device exerting vacuum pressure on the other side of the filter of less than about 4 mm of Hg. The system is particularly useful for determining impurities in water.