The vats are also provided with false bottoms, outlet cocks, steam pipes and so forth.
Both fixed and rotating vats are employed, the chlorination proceeding more rapidly in the latter case; rotating barrels are sometimes used.
Moreover, the high potential difference between the terminals of the series tank introduces a greater danger of shortcircuiting through scraps of metal at the bottom of the bath; for this reason, also, lead-lined vats are inadmissible, and tarred slate tanks are often used instead.
It consists of a number of tanks or " vats," placed at the same level and connected by pipes which reach nearly to the bottom of one tank and open out at the top into the next tank.
The wet alkali-waste as it comes from the lixiviating vats, is transferred into upright iron cylinders in which it is systematically treated with lime-kiln gases until the whole of the calcium sulphide has been converted into calcium carbonate, the carbon dioxide of the lime-kiln gases being entirely exhausted.