How does this reaction happen?
At 140°C in the presence of sulfuric acid two molecules of ethanol are dehydrated
(lose a molecule of water) to form ether. The sulphuric acid is
regenerated and reused. Above about 160°C (320°F) ethene is produced
instead, by loss of water from just one molecule of ethanol. Some
sort of temperature control is needed.
As the ethanol and sulfuric acid reacted together ether vapor was given off. It
needed to be cooled to condense it into liquid ether, so the apparatus
was joined to a long tube that went through cold water to a receiver
in a cold water bath. Because ether boils at 34.5°C (94.1°F) it needs
to be cooled to condense it from a gas to a liquid and kept cool
so it remains liquid. Below around 120°C (248°F) the reaction does not
take place, above around 160°C ethene gas instead of ether is
formed, so 140°C was chosen as a compromise between no reaction
and the wrong reaction.
Any experiment with ether
must be carried out in the absence of any open flame.