Pattinsons Process

Pattinson's Process is the method which is usually adopted for desilverising lead, and is so effectual that silver, if present in the lead to the extent of only two or three ounces to the ton, may be profitably extracted. The process depends on the fact that when argentiferous lead is melted and allowed to cool the portions that solidify first are not so rich in silver as the still liquid portion. The lead is hence melted in a number of pots arranged in line, each about five or six feet across. The crystals solidifying first are ladled out and passed into the pot on the right until two-thirds of the lead has been so transferred, the remainder being passed to the left. By this means at the extreme left a highly argentiferous lead is obtained, from which the silver is obtained by cupellation (q.v.).