Did you know that Ho Wood, Ravintsara and Camphor oils all come from the same plant?
Cinnamomum camphora is a large evergreen tree native to Asia and occurs in many chemotypes, three of which are commercially processed. Paradoxically, White Camphor oil, commonly known as “Camphor Oil” contains very little camphor. Strictly speaking it is not a true essential oil, it is a fraction. After camphor (the constituent) is separated by filtration, the residual essential oil is fractionally distilled producing these four fractions. White Camphor “oil” is one that is used in aromatherapy. The Yellow and Brown fractions are high in safrole and are not usually sold on the open market. The Blue fraction is not sold at all. None of these contain very much camphor (up to 9%, more typically 3%).
More on fractionation here: https://en.wikipedia.org/wiki/Fractional_distillation
Ho Wood oil is rectified to reduce the safrole content. Safrole is a carcinogen.