Can someone explain me the difference in boiling point of water when I add: KBr; CaCl2; AlCl3?

I have noticed (during an experiment) that the boiling point of the solutions created by H2O+KBr; H2O+CaCl2 and H2O+AlCl3 see their boiling point increase.


During the experiment, I thought that, since every time the number of Ions dissociated in each solution increases, the boiling point of each solution should increase with the number of Ions formed: BP(H2O+AlCl3)>BP(H2O+CaCl2)>BP(H2O+KBr)


But apparently this is true only when the concentration of the salt in the water is small: in fact, with high concentrations, the solution formed by CaCl2 reaches much higher boiling points than the one formed by AlCl3. 


Is there someone who can help me to understand?


