Editing Weldon process

The '''Weldon process''' is a process developed in 1866 by [[Walter Weldon]] for recovering [[manganese dioxide]] for re-use in [[chlorine]] manufacture.  Commercial operations started at the Gamble works in St. Helens in 1869.  The process is described in considerable detail in the book, The Alkali Industry, by J.R. Partington,D.Sc.

The common method to manufacture chlorine at the time, was to react manganese dioxide (and related oxides) with [[hydrochloric acid]] to give chlorine:

: MnO<sub>2</sub> + 4 HCl → MnCl<sub>2</sub> + Cl<sub>2</sub> + 2H<sub>2</sub>O

Weldon's contribution was to develop a process to recycle the manganese.  The waste [[manganese(II) chloride]] solution is treated with lime, steam and oxygen, producing [[calcium manganite(IV)]]:

: 2 MnCl<sub>2</sub> + 3 Ca(OH)<sub>2</sub> + O<sub>2</sub> → [[Calcium oxide|CaO]]·2MnO<sub>2</sub> + 3 H<sub>2</sub>O + 2 CaCl<sub>2</sub>

The resulting calcium manganite can be reacted with HCl as in related processes:

: CaO·2MnO<sub>2</sub> + 10 HCl → CaCl<sub>2</sub> + 2 MnCl<sub>2</sub> + 2 Cl<sub>2</sub> + 5 H<sub>2</sub>O

The manganese(II) chloride can be recycled, while the calcium chloride is a waste byproduct.{{Citation needed|date=May 2012}}

The Weldon process was first replaced by the [[Deacon process]] and later by the [[Chloralkali process]].

== References ==
{{More citations needed|date=September 2018}}
{{Reflist}}

==Further reading==
*{{cite web |title=The Chlorine industry | website=Lenntech |url=http://www.lenntech.com/Chemistry/chlorine-industry.htm |access-date=11 September 2018}}
*{{cite EB1911 |first=Georg |last=Lunge |wstitle=Alkali Manufacture#Preparation of Chlorine |display=Alkali Manufacture § Preparation of Chlorine |volume=1 |pages=666–66}}
*{{cite book |url=https://archive.org/details/alkaliin8dustry00partuoft |title=The Alkali Industry |first=J.R. |last=Partington |year=1919 |location=London  |publisher=Baillière, Tindall & Cox}}

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[[Category:Chemical processes]]
[[Category:Chlorine]]


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[[de:Walter Weldon#Weldon-Verfahren]]