Provided here are methods of manufacture of viloxazine and its various salts, as well as viloxazine-related compounds, such as novel intermediate reaction products and polymorphs thereof. In particular, the methods provide a substantially pure API of viloxazine HCl while avoiding undesirable impurities. The methods further provide for separating, identifying, and characterizing novel polymorphs of viloxazine. Further provided are methods for synthesis and identification and characterization of novel intermediates of viloxazine, as well as for some important metabolites and precursors of metabolites of viloxazine.