Tar bases are recovered by the use of sulphuric acid. Naphthalene and anthracene are recovered by further distillation or crystallization. These crude chemicals recovered from several refineries are further processed into pure chemicals in secondary plants. Pitch is considered a valuable binder and waterproofer. Pitch and mixtures of pitch and creosote in various proportions constitute road tar and fuels.
Pitch is employed in a number of formulations for treating walls, floors and roofs against damp.
Processing of the simpler chemical substances that are distilled from coal tar are further processed into benzine, toluene and xylene for use as chemicals or solvents. Naphtalene is processed into mothballs and dyestuffs but more interestingly to make phthalic anhydride, in turn to make plasticisers, resins and paints. The oldest specimens of glass date back to the year 2500 BC and are examples of sculpted glass from solid blocks from ancient Egypt. Records indicate that almost a thousand years passed before the Egyptians learnt how to produce glass and ceramic pots by pouring molten liquid over a shaped sand core in successive layers until the vessel was sufficiently sturdy. It was a further thousand years before the development by the Romans of the tool that revolutionised glassworking -the blowing iron.