Two isomers X and Y with the formula Cr(H₂O)₅ClBr₂ were taken for an experiment on depression in the freezing point. It was found that one mole of X gave depression corresponding to 2 moles of particles and one mole of Y gave depression due to 3 moles of particles. The structural formula of X and Y respectively, are: 

1. [Cr(H₂O)₅Cl] Br₂; [Cr(H₂O)₄Br₂]Cl.H₂O

2. [Cr(H₂O)₅Cl] Br₂; [Cr(H₂O)₃ClBr₂].2H₂O

3. [Cr(H₂O)₅Br]BrCl; [Cr(H₂O)₄ClBr]Br.H₂O

4. [Cr(H₂O)₄Br₂]ClH₂O; [Cr(H₂O)₅Cl]Br₂