Mercury is a liquid at 400 degrees Fahrenheit. However, it's important to clarify:

* Mercury is not a state. Mercury is an element.

* 400 degrees Fahrenheit is not a specific temperature for any state. Mercury's melting point is -37.89°F (-38.83°C), and its boiling point is 674.11°F (356.73°C). This means that at 400°F, mercury is a liquid.

So, while Mercury is a liquid at 400 degrees Fahrenheit, it's not specific to a particular state.