JPMorgan Chase announced it has agreed to sell its physical commodities trading unit to the Mercuria Energy Group, a rapidly growing Swiss trading firm, for $3.5 billion in cash. The Volcker Rule, part of the sweeping Dodd-Frank financial regulatory overhaul, restricts the ability of banks to trade for their own accounts. That extends to limits on some commodities trading. The Federal Reserve is also considering limiting banks’ commodities activities to try to reduce their exposure to a potential source of instability. The Commodity Futures Trading Commission has subpoenaed Goldman Sachs and other owners of metals warehouses as part of an investigation into potential irregularities in the aluminum market. JPMorgan, which announced its intent to sell the commodities unit last summer, had held discussions with potential buyers like Macquarie. It had entered talks with Mercuria, a firm founded by two former Goldman Sachs traders that has become one of the world’s four biggest independent commodities trading businesses with offices in 28 countries and employing more than 1,000 people.