Which of the following statements regarding ferric salts is not correct ?

Question

$\begin {array} {1 1} (A)\;\text{In the vapour phase, ferric chloride corresponds to the dimer structure} \\ (B)\;\text{The aqueous solution of ferric salt is alkaline} \\ (C)\;\text{Ferric chloride is used as an antiseptic}\\ (D)\;\text{The formula of ferric alum is $Fe_2(SO_4)_3.(NH_4)_2SO_4.24H_2O$} \end {array}$