Talk:Patio process

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Chemical reaction mechanism

Latest comment: 1 month ago2 comments2 people in discussion

The necessary reduction of Ag⁺ cations into metallic Ag soluble in liquid mercury to form an amalgam first requires a reducing agent to donate its electrons to the Ag⁺ cations. Is Hg itself this reducing agent? And what is the exact role of CuSO₄ in the reduction/amalgamation process of Ag in Hg? Is it acting as a catalyst facilitating the transfer of electrons from Hg to the Ag⁺ ions? Are the Cu²⁺ ions first reduced by Hg into metallic Cu, or Cu⁺ ions, which subsequently could transfer their electrons to Ag⁺ ions? This mechanism has to be elucidated and sourced with reliable references. Please, could you develop the question here and complete the corresponding empty section in the Article page? In advance, thank you very much. Shinkolobwe (talk) 21:15, 21 February 2023 (UTC)Reply

I found this page on UNR's website discussing the patio process, which provides the following:

"water, mercury, salt and roasted copper and iron sulfides were added"

"roasted copper and iron sulfides turn into copper sulfates (CuSO4) and iron sulfates (FeSO4). The salt (NaCl) reacts with the silver sulfide (Ag2S) in the open air and light to form silver chloride (AgCl)"

1) Ag2S + 2NaCl + 2O2 = Na2SO4 + 2AgCl

2) 2AgCl + 2Hg = 2Ag + Hg2Cl2

Admittedly, my knowledge of ionic chemistry is sparse, so I cannot attest to the correctness of the equations above, but given the presence of sulfates on the products side, it seems like the copper is consumed, so it is not catalytic (at least as I understand it). However, toward the latter points you make, it seems like the sulfates are reacting with the brine to produce AgCl which would seem to indicate that Hg is the reducing agent.

Additionally, for a more formal academic source, please see here.

I have not edited wikipedia in the past, and am interested in this topic for academic research, but at present do not have plans to update this article, but hopefully provide some first resources for those that might 130.184.252.72 (talk) 19:13, 13 August 2024 (UTC)Reply

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