Everything is soluble in everything else; "nth" principle of physical chemistry.
Here's another fundamental principle of physical chemistry. My thesis adviser spent much of his career studying the surface physics of alkali halides. He chose this vocation with the idea that here at least is a system so simple, so uncomplicated he could surely eventually understand everything there is to know about it. 40 years later they were still surprising him. But he did discover this fundamental principle of physical chemistry "Every even moderately plausible mechanism you can dream up happens to some degree. Most of the implausible ones also happen."