© Oxford University Press 2011 IC3.6.4 The Leblanc process The Leblanc process.

© Oxford University Press 2011

IC3.6.4 The Leblanc process

The Leblanc process



Nicolas Leblanc. The French chemist who

invented a process for making alkali from

salt and limestone.

Using this process, an alkali industry grew

up in the 1800s in Widnes, Northwest

England.



Pollution over Widnes

in 1895.

Leblanc’s process produced lots of waste.

In 1862, nearly 2 million tonnes of raw materials were

used to produce just a quarter of a million tonnes of

product. The rest was waste.

For every tonne of salt used, three tonnes of coal

were burned.



The Leblanc process

salt(sodium chloride)

hydrogen chloride gas

coal(carbon)

limestone(calcium carbonate) solid waste

(calcium sulfide)

alkali - soda ash

(sodium carbonate)

sulfuric acid from pyrites (iron sulfide)

salt cake(sodium sulfide)



A polluting process

1 tonne

of alkali

0.75 tonnes 2 tonnes

hydrogen chloride solid waste



By 1891, over 200 hectares around Widnes were buried under an average of

4 metres of solid waste from the alkali industry.

Hydrogen chloride, from the factory chimneys, dissolved in rainwater to produce

acid rain.

The acid rain damaged buildings and wildlife. It also reacted with the solid waste to

release foul-smelling hydrogen sulfide gas.



The 1863 Alkali Act limited

emissions of hydrogen

chloride gas.

William Gossage invented a

way of removing hydrogen

chloride from the chimney

gases produced by the alkali

factories.

The process produced

hydrochloric acid which was

then put down the drain!

Cleaning up the process

hydrogen chloride gas from furnaces

water trickling down

hydrochloric acid

tower packed with coke




In 1874, Henry Deacon invented a way to use

the hydrogen chloride gas to make chlorine.

In the process, hydrogen chloride gas is

oxidised to produce chlorine, a useful product.

oxygen

hydrogen

chlorine




The problems of the Leblanc

process were solved by

developing new methods for

manufacturing alkalis.

Widnes1895

Widnes 2010

© Oxford University Press 2011 IC3.6.4 The Leblanc process The Leblanc process.

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Transcript of © Oxford University Press 2011 IC3.6.4 The Leblanc process The Leblanc process.