Methods of Preparation
of deuterium
1. By Diffusion
Process: It is possible to obtain deuterium directly from hydrogen gas by taking advantage
of different rates of diffusion of the two isotopes. The lighter hydrogen
diffuses more quickly than deuterium through a porous partition under reduced
pressure. Lower the pressure, higher is the efficiency of the process.
The process of diffusion has been carried out in various diffusion
chambers called Hertz diffusion units. Each diffusion units consists of a
porous membrane.
When the
mixture is led into the diffusion units under reduced pressure by the help of
mercury diffusion pumps, the heavier deuterium diffuses less readily while
lighter hydrogen diffuses at faster rates. This process is repeated several
times till hydrogen gets collected on the left while deuterium on the right.
The efficiency of this process could be increased by increasing the number of
diffusion units.
By fractional
distillation of liquid hydrogen: By
fractional distillation of liquid
hydrogen, it is possible to result in enrichment of the last fraction in
deuterium because deuterium boils at 23.5K while hydrogen boils at lower
temperature of 20.2K.
By electrolysis of
heavy water: As water contains about one part of heavy water in 6000 parts, at
first, the concentration of heavy water is increased by fractional electrolysis
of water containing an alkali between nickel electrodes. For example 1 ml of
heavy water is obtained from about 20 litres by this method.
From heavy
water, it is possible to get deuterium by decomposing it with sodium, red hot
iron or tungsten or by its electrolysis containing sodium carbonate.
2D2O ->Electrolysis® 2 D2 + O2
Deuterium
D2O + 2Na -> NaOD + D2
Sodium deuteroxide.
Deuterium obtained can be further obtained in purified state by the diffusion
process.
Physical properties
Like hydrogen, deuterium is a colourless, odourless and tasteless gas
which is insoluble in water and bad conductor of heat and electricity. The
values of boiling point, melting point, vapour pressure, dissociation energy
and latent heat of fusion are found to be lower for protium than deuterium.
Chemical properties
By virtue
of its larger mass, deuterium reacts slower than hydrogen.
1. Burning in oxygen: Like hydrogen, it is combustible and burns in oxygen or air to give deuterium oxide which is also known as heavy
water.
2 D2 + O2 ->
2D2O.
2. Reaction with
halogens: Like hydrogen, it combines with halogens under suitable conditions to form
their deuterides.
D2+ Cl2 --- (in light
Deuterium chloride) ---- > 2 DCl
D2+ F2 ---- ( in dark
Deuterium fluoride )---- > D2 F2
3. Reaction with
nitrogen: Like hydrogen, it combines with nitrogen in the presence of a catalyst to form
nitrogen deuteride which are also known as heavy ammonia or deutero ammonia.
3D2 + N2 - > 2ND3
4. Reaction with
metals: Like hydrogen, it reacts with alkali metals at high temperatures (633K) to form
deuterides
2 Na + D2 -- > 2 NaD
5. Addition reactions: Like hydrogen, it gives addition reactions with unsaturated compounds. For example, a mixture of deuterium and
ethylene when passed over heated nickel, gives Ethylene deuteride which is
saturated hydrocarbon like ethane.
C2H4
+ D2 --- (Ni , 535K) à CH2D -CH2D
Exchange reactions: Deuterium and hydrogen atoms undergo
ready exchange with H2, NH3, H2O and CH4 deuterium slowly exchanges their
hydrogens partially or completely at high temperatures.
H2 + D2 -><- 2 HD
2NH3 + 3D2
àß- 2ND3 + 3H2
H2O + D2 àß- D2O + H2
CH4 + 2D2 àß- CD4 + 2H2
C2H6 + 3D2 àß- C2D6 + 3H2
Uses of deuterium
It is used as tracers in the study of mechanism of chemical reactions.
High speed deuterons are used in artificial radioactivity.
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