Abstract: Silver is recovered from photographic waste liquids containing emulsified silver, silver compounds, and gelatin by reacting therewith a proteolytic enzyme while the reactants are maintained in an alkaline condition. Then the reactants are acidified to a pH of 4.2 or less by introducing an acid such as HCl or H.sub.2 SO.sub.4. Precipitation of gelatin-bound silver and silver compounds occurs upon acidification, and the precipitate is allowed to settle out in a settling tank. Supernatant liquid is removed from the top, neutralized and sent to sewer. Settled sludge is removed from the bottom and silver recovered, as by incineration. The operation can be conducted either batch-wise or continuously.

Abstract: This invention provides a process for separating metal values from an anhydrous mixture of metal halides in a fluid state, i.e. vapor or liquid; the separation is made by contacting a fluid mixture containing a halide of at least one less-noble metal selected from the group consisting of iron and manganese, and a halide of at least one more-noble metal selected from the group consisting of copper, cobalt and nickel, with an elemental metal. This procedure is especially effective in the refining of ocean floor nodule ores.

Abstract: Ammonium polyphosphates having a major portion of the P.sub.2 O.sub.5 content thereof in the form of condensed phosphates are prepared by reacting wet-process phosphoric acid directly with ammonia under specified conditions. It is demonstrated that exchange and recovery of heat from the hot ammonium polyphosphate reaction mixture is critical to allow production of ammonium polyphosphate solutions from orthophosphoric acid and ammonia with polyphosphate contents high enough for chelating inherent impurities during extended periods of storage. Moreover, the present invention avoids substantial corrosion of the equipment.