Pure silver is seldom found outside of a jewelry store, but impure silver is all around, and those impurities can be refined out rather easily, provided you take all the necessary precautions. Refining silver without resorting to the use of a large smelting oven requires the use of nitric acid, so safety is still as important, if not more so, than it would be when using an oven.
Weigh the silver you are going to be refining. You will need 150 ML of concentrated nitric acid for every ounce of metal.
Put on your safety gear. Nitric acid is extremely caustic, and can cause permanent damage if it comes in contact with your skin.
Put the silver into one of the five-gallon buckets, then measure out and pour the appropriate amount of nitric acid onto the silver as specified by the weight. The silver will react violently to the acid, and will foam up and bubble for several minutes as it is dissolved, so ensure that the bucket is only about 1/3 full of metal before pouring the acid. Stir the bucket periodically to speed the dissolving process.
Wait for the silver to completely dissolve into the acid, and for the acid to stop bubbling and foaming. Once this has happened, pour the contents of the bucket through the filter and into the second bucket. The filter will prevent the impurities left behind from going into the second bucket.
Add the silver precipitant crystals to the acid at a rate of one ounce for every 40 ounces of dissolved silver. As the crystals are added, the dissolved silver will bond to the crystals and form pure silver lumps that will sink to the bottom of the bucket.
Wait for 30 to 45 minutes for the silver to completely form with the crystals.
Pour the acid back through the filter into the first bucket, then pour soda ash into the acid to neutralize it.
Rinse the pure silver thoroughly with tap water, then place one to two drops of aqua ammonia onto the surface of the silver and rub it all around. If any of the silver shows traces of a bluish tint, rinse again and repeat the test. Do this until no blue shows up.
Rinse the silver one final time in distilled water to remove any trace particulates, then leave it to air-dry.