Home Tour Physics Chemistry Earth Science Environment Scams Lesson Plans
Introduction Ore Processing Fire Assaying

Previous The Washoe Process Next

In the Washoe Process (named for Indians that inhabited the area around Lake Tahoe, and thus the name for the area around Virginia City, the name now preserved in the name of the neighboring county, Washoe County), the improvement to the process of heating the ore during extraction in an iron pan increased the recovery and decreased the processing time.  The iron from the pan acted as the reducing agent for the silver:

2AgCl + Fe = 2Ag + FeCl2

The drive for this reaction is nearly 0.6 volts greater than the drive for the reaction for reducing silver using copper (at standard conditions as above), so this reaction is highly favored.  

In addition, heating the reaction mixture helped the  formation of the amalgam of silver with mercury.  In this reaction, the mercury was not changed into mercurous chloride (calomel), so mercury was not used up in the process.  The iron pans and iron mixers (mullers) would be consumed in the process, but these could be replaced readily.

The photo of the interior of a mill on the Comstock shows the heated iron vats in which the silver ore from the mines is stirred with the copper sulfate, salt and mercury. The vats are mounted on a hillside on various levels so the resulting solution can be gravity fed to the next step in processing. This photo shows the Brunswick mill at the far right in the middle with a shoot leading to a tailings pond and a dammed up Carson River and water flume to the left. The river would have provided the water as well as washing away wastes, a practice that would not be allowed in modern mining. The railroad for bringing in the raw ore and taking out the processed gold and silver is just to the left of the mill.

The left photo is of the interior of a mill on the Comstock using the Washoe Process. The right photo shows the exterior of the Brunswick Mill on the Carson River.

(Reference:  Dennis, W.H., A Hundred Years of Metallurgy, Gerals Duckworth & Co., Ltd., London, 1963, p. 282-287)

Previous The Washoe Process Next


Home Tour Physics Chemistry Earth Science lEnvironment Scams Lesson Plans