The vats are also provided with false bottoms, outlet cocks, steam pipes and so forth.
For open pools and dams Schenck substitutes large wooden vats under cover, into which the flax is tightly packed in an upright position.
In spite of all precautions a certain quantity of impurities is always formed, but this should be kept down as much as possible by strictly watching the temperature in the vats and by taking care that the black-ash in the wet state is never exposed to the air.
Both fixed and rotating vats are employed, the chlorination proceeding more rapidly in the latter case; rotating barrels are sometimes used.
chlorate used in the vats also produced a positive reaction (Stauffer 1931 ).