Coal tar is a brown or black liquid of extremely high viscosity. Coal tar is among the by-products when coal is  carbonized to make coke or gasified to make coal gas. Coal tars are complex and variable mixtures of phenols, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic compounds.

Coal tar is a brown or black liquid of extremely high viscosity. Coal tar is among the by-products when coal is  carbonized to make coke or gasified to make coal gas. Coal tars are complex and variable mixtures of phenols, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic compounds.