When writing a modern Sonnet is it acceptable to separate the 3 quatrains with white space?

Yes!  Sonnets have one of the most prescribed structures of all types of poetry.  Defined,
sonnets contain 14 lines of iambic pentameter and follow one of two schools which differ
slightly in rhyme scheme:  ABAB, CDCD, EFEF, GG or ABAB BCBC CDCD EE.  Of the two schools, the
first given style traditionally reflects three different views on a particular...