Wikipedia
Black liquor
In industrial chemistry, black liquor is the waste product from the kraft process when digesting pulpwood into paper pulp removing lignin, hemicelluloses and other extractives from the wood to free the cellulose fibers.
The equivalent material in the sulfite process is usually called brown liquor, but the terms red liquor, thick liquor and sulfite liquor are also used.
Usage examples of "black liquor".
Notwithstanding my limp and the quantity of black liquor I had drunk, I felt no fear, only excitement, as in the days when I'd merrily baited the bucks of the herd.