The black soil sample mostly contains the organic matter, chalk and quartz. It is necessary to measure the relative weight of SiO2 particles that are 2.5 μm or less.
To do that the organic matter and chalk were dissolved by additional chemicals and then the sample was filtered through the paper filter and dried. Then the dried part of the sample was weighted and Mastersizer 3000E laser diffraction particle size analysis instrument was used to measure the sizes of particles in it.
The measured relative number of particles with size from 2.5 μm to 0.6 μm was 3.6% But Mastersizer 3000E did not find any particles smaller then 0.6 μm perhaps because they went through the paper filter into the filtered out solution.
The question is how to catch that particles that are smaller then 0.6 μm in this case ? Which filter or process can be used to collect and return them to that dried part of the sample ?