International Dyestuff Industry - ColorantsHistory.Org

Figure 4. Chlorine Ovens. Edelstein Collection, Hebrew University.
The end manholes were slabs of wood covered with lead. The ovens were charged through
openings at dd (b in the cross section), and the lids to these were made airtight with a
liquid seal of "chlorine oils," the residual oil from the reaction, which was placed in the door
channels. Lead piping was used to deliver the chlorine and carry away hydrochloric acid and
unreacted chlorine from the last stages of the chlorination. Since this caused loss of the
valuable reagent, the ovens were then operated in pairs so that outgoing gas from the first
oven was then passed into the second.
The next day a new charge of anthracene was placed in the first oven, the incoming gas
was then directed into the second oven, to complete chlorination, and then passed through
the fresh charge. By this continuous alternation in the supply of chlorine, losses were
minimized.
A steam chamber was built into the surrounding brickwork to maintain the desired
temperature. Hydrogen chloride gas was recovered for re-use by condensation in coke
towers. Wooden tools were used to loosen the crystalline dichloroanthracene remaining in
the oven, which was then transferred to tubs and broken up in the presence of caustic soda
which neutralized the hydrochloric acid. The product was afterwards separated from the
solution and hydraulically pressed between linen cloths to remove unwanted materials as
the “chlorine oils.”
The resulting crystalline cake then underwent further purification by repeated breaking up,
soaking in coal tar naphtha, and pressing. Any residual naphtha was recovered by steam
treatment. Finally, the product dichloroanthracene was dried on trays in a drying room and
was found to be about 84 per cent pure.
In the important sulfonation step, the dichloroanthracene was treated with sulfuric acid in
iron pots, each capable of holding about 30 gallons of liquid, and fixed in place in rows
above ovens. The whole arrangement was surrounded by brickwork to retain heat (Perkin’s
Figure 5).