[Assembler]

Does anyone know why aluminum sulfate reagent wouldn't dissolve in water?  It's supposed to be soluble in water up to 86 g/100mL at room temperature.  I feel like I'm missing something obvious, but I checked the chemical label and I made sure I was using water.  I borrowed it unused from another lab, and it is about 3-4 years old.

I did try making it up in 0.1 N HCl, but still not soluble

Uggh.  Nevermind.  Just heated it up and it when into solution.