It can be seen
that the selectivity decreases with increasing frother
dosage for C4E1, C4E3 and C6E2 and increases for C2E2
and remains constant or slightly increases for C4E2. It
confirms that the used ethers form two groups of
reagents. One of them is a group of the C4E1, C4E3 and
C6E2 ethers, which provide the best selectivity of
separation between shale and quartz, especially at low
concentrations.