Weldon process
Encyclopedia
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 describe in considerable detailed 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:
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):
The resulting calcium manganite can be reacted with HCl as in related processes:
The manganese(II) chloride can be recycled, while the calcium chloride is a waste byproduct.
The Weldon process was first replaced by the Deacon process
and later by the Chloralkali process
.
Walter Weldon
Walter Weldon was an English chemist, journalist, and fashion publisher.-Family:He was brother to Ernest J. Weldon, founder of Weldon & Wilkinson Ltd...
for recovering manganese dioxide for re-use in chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
manufacture. Commercial operations started at the Gamble works in St. Helens in 1869. The process is describe in considerable detailed 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:
- MnO2 + 4 HCl → MnCl2 + Cl2 + 2H2O
Weldon's contribution was to develop a process to recycle the manganese. The waste manganese(II) chloride
Manganese(II) chloride
Manganese chloride describes a series of compounds with the formula MnCl2x, where the value of x can be 0, 2, or 4. The tetrahydrate is the most common form of "manganese chloride". MnCl2·4H2O, but the anhydrous form and dihydrate MnCl2·2H2O are also known...
solution is treated with lime, steam and oxygen, producing calcium manganite(IV):
- 2 MnCl2 + 3 Ca(OH)2 + O2 → CaOCalcium oxideCalcium oxide , commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature....
·2MnO2 + 3 H2O + 2 CaCl2
The resulting calcium manganite can be reacted with HCl as in related processes:
- CaO·2MnO2 + 10 HCl → CaCl2 + 2 MnCl2 + Cl2 + 5 H2O
The manganese(II) chloride can be recycled, while the calcium chloride is a waste byproduct.
The Weldon process was first replaced by the Deacon process
Deacon process
The Deacon process was a secondary process used during the manufacture of alkalis by the Leblanc process. Hydrogen chloride gas was converted to chlorine gas which was then used to manufacture a commercially valuable bleaching powder, and at the same time the emission of waste hydrochloric acid...
and later by the Chloralkali process
Chloralkali process
The chloralkali process is an industrial process for the electrolysis of sodium chloride solution . Depending on the method several products beside hydrogen can be produced. If the products are separated, chlorine and sodium hydroxide are the products; by mixing, sodium hypochlorite or sodium...
.