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The process has a high energy consumption, for example around 2,500 kWh (9,000 MJ) of electricity per tonne of sodium hydroxide produced. Because the process yields equivalent amounts of chlorine and sodium hydroxide (two moles of sodium hydroxide per mole of chlorine), it is necessary to find a use for these products in the same proportion ...
Chlorine can be manufactured by the electrolysis of a sodium chloride solution , which is known as the Chloralkali process. The production of chlorine results in the co-products caustic soda (sodium hydroxide, NaOH) and hydrogen gas (H 2). These two products, as well as chlorine itself, are highly reactive.
In the process, sodium hypochlorite (NaClO) and sodium chloride (NaCl) are formed when chlorine is passed into a cold dilute sodium hydroxide solution. The chlorine is prepared industrially by electrolysis with minimal separation between the anode and the cathode.
If the solution near the anode is acidic then it will contain elemental chlorine, if it is alkaline then it will comprise sodium hydroxide. The key to delivering a powerful sanitising agent is to form hypochlorous acid without elemental chlorine - this occurs at around neutral pH. Hypochlorous is a weak acid and an oxidizing agent. [3]
In the process, sodium hypochlorite (NaClO) and sodium chloride (NaCl) are formed when chlorine is passed into cold and dilute sodium hydroxide solution. The solution must be kept below 40 °C (by cooling coils) to prevent the undesired formation of sodium chlorate. Cl 2 + 2 NaOH → NaCl + NaClO + H 2 O From Sodium chlorate#Synthesis:
In addition, a rocking mechanism (B shown by fulcrum on the left and rotating eccentric on the right) agitates the mercury to transport the dissolved sodium metal from the outside cells to the center cell. The anode reaction in the center cell takes place at the interface between the mercury and the sodium hydroxide solution.
All endeavours to obtain either hydrochloric acid or free chlorine in the ammonia-soda process have proved commercial failures, all the chlorine of the sodium chloride being ultimately lost in the shape of worthless calcium chloride. The Leblanc process thus remained the sole purveyor of chlorine in its active forms, and in this way the fact is ...
The product of the process, sodium hypochlorite, provides 0.7% to 1% chlorine. Anything below the concentration of 1% chlorine is considered a non-hazardous chemical [according to whom?] although still a very effective disinfectant. The sodium hypochlorite produced is in the range of pH 6-7.5, relatively neutral in regards to acidity or