Gold, silver, and platinum group metals are widely used in electronic and electrical components to provide long-term reliability, Construction of military equipment consumes the largest proportion of the precious metals used in the electronic and electrical industry. Due to obsolescence and damage, military electronics are presently being scrapped at the rate of about 15,000 tons per year. This scrap averages approximately 100 troy ounces of silver, 5 troy ounces of gold, 1 troy ounce of palladium, and lesser amounts of other precious metals per ton.
The high level of development and use of military electronic hardware that soon becomes obsolete assures an expanding supply of scrap electronic components from military sources.
Because of its highly variable and complex nature, military electronic scrap is practically impossible to sample and analyze for metal content. This fact coupled with the inflexibility of presently used scrap-processing methods, limits disposal to a relatively small part of the scrap that is now generated and has been accumulated by military reclamation operations. The Bureau of Mines is currently investigating alternative methods for efficient, low-cost recovery of the precious and base metals in diverse mixtures of military electronic scrap.
Leaching techniques were tried initially for processing the electronic scrap. Nitric acid