The Biological Role of Hydrogen

The plasma must also have a high density for a sufficient time to permit the fusion reaction to occur. Laser heating of frozen deuterium-tritium pellets confined in a magnetic field is a method that has been tested. The neutrons formed react with lithium in an outer mantle, a reaction in which new tritium is formed. This reactor type is called Tokamak and is used in research projects in the USA and England. Similar reactors are used in France, Russia and Japan. 

In the hydrogen bomb the DT-reaction is also essential. In practice lithium deu-teride, LiD, and some tritium are used. Very high temperature and pressure are necessary for the fusion reaction to start. It is obtained by letting a conventional atomic bomb (a fission bomb), combined with the thermonuclear fuel, explode. At this fission reaction tritium is also generated. 

Hydrogen is one of the elements that dominate Kving systems. It is present there free as hydrogen ion, or bound in water and in complex organic molecules. The binding may be conventionally covalent or with special hydrogen bonds. 

In substances that are composed of non-polar molecules such as dimethyl ether CHj-O-CHj and dipropyl ether CjH -O-CjH, strong covalent bonds act between the atoms in the molecules. An individual molecule is, however, loosely bound to another by very weak so-called van der Waals forces. These cannot keep the molecular aggregates together when the material is heated. Melting and boiling points are relatively low but increase with the molecular weight as is exemplified in Table 9.3. 

Substance Formula Molecular weight Melting point C Boiling point °C 

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