Patio process

In the late fifteenth century AD mercury was successfully used as a treatment for syphilis. In the late sixteenth century the development of the Patio process for the recovery of silver by amalgamation (see Silverand silveralloys) greatiy increased the consumption of mercury. Usage of mercury increased in 1643 when Torricelli invented the barometer, and again in 1720 when Fahrenheit invented the mercury thermometer. Other scientific and medical appHcations foUowed. Industrial usage after 1900, particularly in electrical appHcations, expanded rapidly, offsetting the sharp decline in its use in amalgamation. 

The Mexican method referred to by Father de Acosta and Baron von Humboldt was the cold amalgamation, or patio, process introduced at Pachuca by Bartolome de Medina about the middle of the sixteenth century. As early as March 4, 1552, the governing princess (Princesa Gobemadora) in Valladolid acknowledged an urgent request for mercury to be used in the exploitation of silver (28). In this process, salt, mercury,... 

In the patio process the finely ground ore is mixed in a patio or paved courtyard with mercury, common salt, and a mixture of copper and iron sulphates called magistral, prepared by roasting copper pyrites. The ore-heap or torta is kept moist. The reactions involved are obscure and complex, but it is supposed 1 that some of them can be represented thus ... 

The pan-amalgamation process has found more favour than the patio process. The ore in the form of fine sludge is stirred in iron pans with a mixture of mercury, common salt, and cupric sulphate. When the action is complete, the excess of mercury is drained off, and the amalgam is allowed to settle, and then decomposed by heat. In the Boss system the process is continuous, a series of pans and settlers being employed. Some silver ores, notably those containing sulphides of arsenic, antimony, copper, iron, and zinc, are roasted with common salt before amalgamation. 

Patio [Spanish, a courtyard] A medieval process for extracting silver from argentite, Ag2S. The ore was mixed with salt, mercury, and roasted pyrites, which contains cupric sulfate. This mixture was crashed by stones dragged by mules walking on the paved floor of a courtyard. The overall reactions are ... 

This is a variation of the Patio and Cazo processes. Invented around 1860 at the Comstock mines, Nevada, and named after the district where it was developed. Mark Twain described the operations in his autobiographical novel Roughing It (Vol. 1, Chap. 36). 

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