Re: Is there something that can raise the freezing point of water?

     I know of no substance that will raise the freezing point of water. In 
general, impurities of any sort will decrease the freezing point. Further 
discussion can be found in most high school or college level general chemistry 
textbooks.

     Physical changes such as pressure alteration can change the freezing 
point. Because water expands as it freezes, a lower pressure will increase the 
temperature at which water freezes. (Conversely, increased pressure will 
decrease the freezing point of water.) Water is unusual in this respect because 
most substances will experience an increase in their freezing point as pressure 
increases.

     Phase diagrams, again, found in most high school or college general 
chemistry texts, illustrate the relationship between solid, liquid, and gas 
phases as temperature and pressure change.