Abstract: A self-contained portable device for quickly and efficiently recovering a precious metal, such as gold, from bimetallically coated substrate material, such as printed circuit board connectors or tabs. The base metal to which the desired precious metal is bonded must be soluable in nitric acid and be partially exposed. The device includes a processing chamber into which the material to be processed is placed. An etching solution, having a prescribed composition that typically includes nitric acid and at least one effervescent compound, is used to dissolve away the base metal, causing a tunneling effect to free the desired precious metal. Selected agitation, coupled with the frothing action of the effervescent compound(s), greatly enhance the rate at which the precious metal is freed from the bimetallic material. Recirculation of the etching solution from a storage tank to the processing chamber, and vice versa, allows a relatively small amount of the etching solution to be used.

Abstract: A method of strengthening glass comprising heating the glass to a temperature between approximately 700.degree. F. and the decomposition temperature of a selected fatty acid, and applying said fatty acid to the surface of the glass. The fatty acid, in regard to the carboxyl group, employed in the disclosed process is not reacted with any other chemical; it is chemisorbed on the surface of the glass for strengthening the microcrack structure on said surface.