Purifying the product is easily achieved by washing with
toluene, which dissolves anthracene but does not dissolve any
significant quantity of anthraquinone. Our experience has been
that there is always some anthracene present, so to save time and
reduce handling losses, we have the students wash their product
once with toluene before they perform the first TLC. Although
we decided to use TLC on silica gel to detect when the product
was pure anthraquinone, many instrumental techniques could be
used to quantitatively determine the composition of the reaction
product, which would allow for the percent conversion of
anthracene to be determined.