In diethyl ether (C 2 H 5 — —C 2 H 5 ) oxygen atom has two lone pairs of electrons, thus acts as lewis base while in anhydrous AICI 3 aluminium has vacant 3p-orbital of valence shell and thus acts as Lewis acid. AlCl 3 accepts a lone pair of electrons from diethyl ether to complete its octet forming a complex . Hence, anhydrous AICI 3 is more soluble in diethyl ether by means of solvolysis in comparison to hydrous AICI 3 (i.e., AICI 3 . 6H 2 O). Hydrous AICI 3 is a polar compound, while ether is non-polar, so on basis of Thumb`s rule, like dissolve in like solvents. Hence hydrous AICI 3 is least soluble in ether.