This group of collectors comprises a large number of products, which consist essentially of a mixture of mono and diesters of phosphoric acid. They differ in their non-polar hydrophobic radical that can be either aliphatic or aromatic. The non-polar group of the hydrocarbon radical is attached to the polar group via an oxygen bridge. Another group of these reagents is half esters, which were originally developed by Mechanobre and used for flotation of apatite. They are regarded as strong collectors and can be used in either alkaline medium (flotation of apatite and scheelite) or in an acid medium for flotation of titanium minerals (ilmenite, rutile and perovskite). A similar group of collectors called phosphoten was also developed by Mechanobre and consists of 25% of pentavalent phosphorus and 75% naphthenic acid. The resulting reaction product is a powder with a specific gravity of 0.9 g/cm3. This product is soluble in alcohol but not in water. This reagent was used for flotation of zircon, cassiterite and pyrochlore at pH values of 4 10.5.
