Methods in the Manufacture of Chlorine

Chlorine was at first produced commercially by the reaction of sulphuric acid, sodium chloride and black oxide of manganese. Later on when Leblanc s method for the production of soda ash was developed, in the first stage of which hydrogen chloride is a by-product, hydrochloric acid was used instead of sodium chloride and sulphuric acid. This process was carried out in stoneware or porcelain vats which were steam heated from the outside. Reaction between manganese dioxide and hydrochloric acid proceeds in two stages  

Great progress was made when Weldon invented a method for recovering manganese dioxide from waste liquors. By this method calcium hydroxide was added to the liquors which remained after oxidation of hydrochloric acid- 

The precipitated slurry, containing CaO. 2MnOa, called the Weldon mud was then used instead of black oxide of manganese fer the oxidation of hydrochloric acid. This reaction which was carried out in sandstone containers with steam fed into the reaction mixture proceeded according to the equation  

2MnOa + 10HC1 = 2Cla + 2MnCla + CaCla + 5Ha0. (XI-5) 

The utilization of hydrochloric acid amounted to 40% a maximum, the rest being lost as calcium chloride. 

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