A method for the flotation of sulfide ores is disclosed. The method
comprises contacting the sulfide ores with a composition comprising at
least one compound of the formula ##STR00001## where R.sup.1, R.sup.2
and R.sup.3 independently of one another are alkyl groups having 1 to 18
carbon atoms, alkenyl groups having 2 to 18 carbon atoms, aryl groups
having 6 to 10 carbon atoms, or alkylaryl groups having 7 to 10 carbon
atoms. Also disclosed is the process for preparing the above compound.