I would interprete these numbers as: 6 times extraction with 50 ml petroleumether, 3 times with 50 ml ethylacetate and 3 times with 50 ml n-butanol.

I doubt whether 6 extrations is essential. I learned that after 3 extractions (nearly) all has been removed.

I would interprete these numbers as: 6 times extraction with 50 ml petroleumether, 3 times with 50 ml ethylacetate and 3 times with 50 ml n-butanol.

I doubt whether 6 extrations is essential. I learned that after 3 extractions (nearly) all has been removed.

In addition to the reply above, note the order going from hexane (non-polar) to n-butanol (more polar).

I think it is better to make communication with the corresponding author for this article .

Thank you for all..

That is, the number of extraction times X (in) the volume of the solution used for extraction

Thank you doctor @Luay Abed