The solution of silver nitrate is diluted with water and allowed to cool. At this moment, a concentrated solution of sodium chloride is added to precipitated silver. When all the silver has been precipitated as chloride, the mass is allowed to settle and the clear solution containing base metals is drawn off. The precipitate is filtered and washed several times with hot water to dissolve the remaining lead. The silver chloride is treated with granulated zinc and water acidulated with sulphuric acid. Approximately 15 -16 kg of granulated zinc is needed to reduce 45-50 kg of silver from the chloride. The reduction process is slow due to zinc reacts with silver chloride, the addition of sulphuric acid accelerates the reaction, but part of the zinc is attacked by the acid and the formation of hydrogen is favored. Hydrogen helps to reduce silver and part of the success of the reduction process is due to the formation of hydrogen. When the reduction process is complete, the solid and the solution are separated. Silver looks like dark particles, which must be washed, dried, melted and cast in bars. The silver thus obtained is 99.6% to 99.8% pure.
Basically, after drawing off the acid, silver chloride is reduced by the addition of metallic zinc and water acidulated with sulphuric acid to metallic silver, which is very light and spongy. It is filtered, washed for some time so as to free it from any soluble salt and dried. After drying the precipitate is heated and takes a metallic luster. In this moment the material is appropriate for melting and casting.