Heavy Water preparation

Preparation of heavy water : Deuterium oxide \left ( \textrm{} D_{2} \textrm{} O \right ) is called heavy water.

Preparation of heavy water – “Electrolytic method” :

Heavy water can be prepared by the exhaustive electrolysis of water containing alkali according to Taylor, Eyring and Frost process. The process involves seven stages. The electrolytic cell is made of steel which acts as cathode. A cylindrical nickel sheet with holes acts as anode. A large number of cells are used for electrolysis.

In the first stage 3 litres of \frac {\textrm{} N}{2} NaOH solution is taken in an electrolytic cell. It is subjected to electrolysis till the volume of the electrolyte reduces to \frac{1}{6} of its original volume. The alkali present is partly neutralized by passing \textrm {} C \textrm {} O_{2} through the electrolyte.

It is distilled and then electrolysed in a similar way and at the end of the seventh stage 99% \textrm{} D_{2} \textrm{} O is obtained. This on careful fractional distillation gives 100% pure heavy water.

preparation of heavy water in electrolytic method diagram

Chemical Properties of heavy water \left ( \textrm{} D_{2} \textrm{} O \right ) :

Heavy water reacts with nitrides to form deutero ammonia.

\textrm{} M \textrm{} g_{3} \textrm{} N_{2} + 6 \textrm{} D_{2} \textrm{} O \longrightarrow 3 \textrm{} M \textrm{} g\left ( \textrm{} O \textrm{} D \right )_{2} + 2 \textrm{} N \textrm{} D_{3}

Heavy water reacts with carbides forming heavy hydrocarbons. When calcium carbide is treated with heavy water deutero acetylene is formed.

\textrm{} C \textrm{} a \textrm{} C_{2} + 2 \textrm{} D_{2} \textrm{} O\longrightarrow \textrm{} C \textrm{} a\left ( \textrm{} O \textrm{} D \right )_{2} + \textrm{} D - \textrm{} C\equiv \textrm{} C - \textrm{} D    (Deutero acetylene)

It reacts with active metals like Na and Ca and liberates deuterium.

2 \textrm{} N \textrm{} a + 2 \textrm{} D_{2} \textrm{} O \longrightarrow 2 \textrm{} N \textrm{} a \textrm{} O \textrm{} D + \textrm{} D_{2}     (Deutero sodium hydroxide)

\textrm{} C \textrm{} a + 2 \textrm{} D_{2} \textrm{} O \longrightarrow \textrm{} C \textrm{} a\left ( \textrm{} O \textrm{} D \right )_{2} + \textrm{} D_{2}    (Duetero calcium hydroxide)

Heavy water reacts with aluminium chloride forming aluminium deuteroxide. The process is called deuterolysis.

\textrm{} A \textrm{} l \textrm{} C \textrm{} l_{3} + 3 \textrm{} D_{2} \textrm{} O \longrightarrow \textrm{} A \textrm{} l\left ( \textrm{} O \textrm{} D \right )_{3} + 3 \textrm{} D \textrm{} C \textrm{} l

Uses of Heavy water \left ( \textrm{} D_{2} \textrm{} O \right ) :

  • Heavy water is used as moderator of neutrons in nuclear reactors.
  • It is used as a tracer compound for studying reaction mechanisms.
  • It is used to study the structure of \textrm{} H_{3} \textrm{} P \textrm{} O_{3} and \textrm{} H_{3} \textrm{} P \textrm{} O_{2}.
  • It is used in the preparation of \textrm D_{2}.