400–430 degrees Celsius heated bath I want to perform a reaction which needs the temperature to be maintained between 400–430 °C. Since it's the only practical solution, I opted for a heated bath.

I'm looking for a hydrocarbon fraction/blend with the boiling point in this range, however, I keep finding conflicting information. If anyone knows such a hydrocarbon product please, let me know.
If it doesn't specifically need to be a hydrocarbon, zinc metal melts at 419.5 °C. Could you do an "ice bath" of zinc chunks in molten zinc, maintaining the melt right at its melting point?