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Heavy Water


Preparation
Ordinary water contains 0.015 per cent of heavy water (D2O), the rest being water. Heavy water is obtained by the electrolysis of ordinary water containing a little alkali till a very small volume is left behind.

Electrolysis of ordinary water is carried out in an electrolytic cell designated by Urey and Co-workers. It consists of a steel cell, 45 cm long and 10 cm in diameter which acts as cathode. A perforated cylindrical sheet of nickel serves as an anode. A number of such cells are used for electrolysis. On electrolysis, water gets electrolysed to give hydrogen and oxygen at a much faster rate than the rate of electrolysis of D2O. Therefore, the concentration of heavy water gradually increases in the residual water. If the electrolysis is carried out repeatedly and for long periods, the residue left behind (unelectrolysed) is almost D2O. In India, heavy water is manufactured in Baroda, Thal (Maharashtra) and Nangal.

Heavy water Plant at Thal (Maharashtra)
 

Many new plants are being set up for the manufacture of heavy water used as moderator in nuclear power plant.  

Property

H2O

D2O

Molecular mass(g mol-1)

18.0151

20.0276

Melting point / K

273.0

276.8

Boiling point / K

373.0

374.4

Enthalpy of formation / kJ mol-1

-285.9

-294.6

Enthalpy of vaporisation(373 K)/KJ mol-1

40.66

41.61

Enthalpy of fusion / kJ mol-1

6.01

--

Temp. of max. density/g cm-3

276.98

284.2

Density (298K)/g cm-3

1.0000

1.1059

Viscosity / centipoise

0.8903

1.107

Dielectric constant

78.39

78.06

Electrical conductivity(293K/Ohm-1 cm-1)

5.7 10-8

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