ClX−:HX2O=1:3\ce{Cl^-} : \ce{H2O} = 1 : 3ClX−:HX2O=1:3。若 v=1v=1v=1：MCl ⋅ 3 HX2O⇒M=29.5\ce{MCl.3H2O} \Rightarrow M = 29.5MCl⋅3HX2O⇒M=29.5（无对应金属）。若 v=2v=2v=2：MClX2 ⋅ 6 HX2O⇒M(水合物)=237.93\ce{MCl2.6H2O} \Rightarrow M(\text{水合物}) = 237.93MClX2⋅6HX2O⇒M(水合物)=237.93，得 M(M)=237.93−70.91−108.09=58.93M(\ce{M}) = 237.93 - 70.91 - 108.09 = 58.93M(M)=237.93−70.91−108.09=58.93 g mol−1^{-1}−1（与钴 Co 相符）。故水合物为 CoClX2 ⋅ 6 HX2O\ce{CoCl2 . 6H2O}CoClX2⋅6HX2O。