Products
Hydrogen is commercially available as compressed gas in compressed gas cylinders. In many countries, it is available from PanGas, for example.
Structure and properties
Hydrogen (H, atomic number: 1, atomic mass: 1.008) is the first and simplest chemical element in the periodic table and the most abundant in the universe. On Earth, for example, it is found in water, in all living things, and in hydrocarbons. Hydrogen is usually present molecularly, i.e. bonded to itself as H2. The sun is composed mainly of hydrogen. Its heat and energy come from the fusion of hydrogen into helium. Hydrogen (protium) consists of only one proton (+) and one electron (-), which it can donate as a valence electron. This with exception of the isotopes deuterium (D, with 1 neutron) and tritium (T, with 2 neutrons). Hydrides are negatively charged hydrogen ions (H–). They are formed with alkali and alkaline earth metals. Examples are sodium hydride (NaH) or calcium hydride (CaH2). Hydrogen exists as a colorless, odorless and extremely flammable gas with a low density. It is apolar, practically insoluble in water, and has a low melting point and boiling point. Hydrogen is non-toxic, but can cause asphyxiation and explosions in higher concentrations.
Reactions
Because of the high binding energy of molecular hydrogen (H-H), chemical reactions usually occur at high temperatures. Oxygen reacts exothermically and explosively with hydrogen. This is known as the oxyhydrogen reaction:
- 2 H2 (hydrogen) + O2 (oxygen) 2 H2O (water)
See also under redox reactions. Conversely, hydrogen and oxygen can be produced by the electrolysis of water:
- 2 H2O (water) 2 H2 (hydrogen) + O2 (oxygen)
When base metals come into contact with an acid, hydrogen is formed:
- Zn (elemental zinc) + H2SO4 (sulfuric acid) zinc sulfate (ZnSO4) + H2 (hydrogen)
With the halogens hydrogen forms acids, for example with chlorine gas (chlorine oxyhydrogen reaction):
- H2 (hydrogen) + Cl2 (chlorine) 2 HCl (hydrogen chloride)
Areas of application
Fields of application in pharmacy (selection):
- Hydrogen is present in most active pharmaceutical ingredients and excipients. This with the exception of some inorganic salts.
- For the catalytic hydrogenation of unsaturated fatty acids in fats and fatty oils (so-called hardening).
- Hydrogen plays a central role in acid-base reactions.
- For chemical syntheses.
Unlike oxygen, hydrogen is of no importance as a medical gas.
