Ok, is that the only way to keep it liquid or can I add some kind of chemical?
This is a common enough noob question on this board. Granted, colligative properties do note that dissolving something in something else produces a freezing point elevation -- the common example, melting ice by adding common salt. Now, DrCMS:
took the time to post the melting point of graphite, ~4500 C, and you're looking for a simple chemical addition, to presumably, completely rewrite the laws of physics, and keep it in a tea kettle, or something. And I'd like to go on record, for you and just about anyone else, that you shouldn't have expected that was likely, even if your particular expertise on the subject is not fully developed yet.