Several Distinguished Scientists have informed me that I am wrong, and that gas will not expand indefinitely, but that it will rise in temperature even when it is unconfined. There is a limit to how much it can expand. Compression heats it and decompression cools it, but only up to a limit. You cannot decompress indefinitely.
Anyway, in the actual Rossi system, you have water transitioning into steam, and that explains why it remains close to 100 deg C despite fluctuations in internal temperature. - Jed
