General
Chlorine has a characteristic penetrating and irritating odor. The gas is greenish yellow in color and the liquid is clear amber. The data on physical properties of chlorine as determined by different investigators show some variations.
Chlorine’s symbol is Cl, its atomic number is 17, and its atomic weight is 35.453. Elemental chlorine almost always exists as a molecule with two chlorine atoms bound together as Cl2. Its molecular weight is 70.906. The CAS registry number is 7782-50-5. At atmospheric conditions, chlorine is a gas.
Liquid chlorine (Cl2) is chlorine which has been cooled and compressed to a liquid form. Under atmospheric temperature and pressure, liquid chlorine evaporates quickly, with one pound of liquid forming about 5.4 cubic feet of chlorine gas.
Liquid chlorine is NOT the same as a hypochlorite or chlorine bleach solutions and this terminology should not be used to describe such solutions
Atomic and Molecular Properties
Atomic Symbol - Cl
Atomic Weight - 35.453
Atomic Number - 17
Molecular Weight of Cl2 - 70.906
Chemical Properties
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Physical Properties |
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Property |
Definition |
Conditions |
Value |
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Boiling Point |
The temperature at which liquid chlorine vaporizes |
14.696 psia |
-29.15°F |
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Critical Density |
The mass of a unit volume of chlorine at the critical pressure and temperature |
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35.77 lb/ft3 |
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Critical Pressure |
The vapor pressure of liquid chloride at the critical temperature |
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1157.0 psia |
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Critical Temperature |
The temperature above which chlorine exists only as a gas no matter how great the pressure |
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290.75°F |
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Critical Volume |
The volume of a unit mass of chlorine at the critical pressure and temperature |
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0.02795 ft3/lb |
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Density |
The mass of a unit volume of chlorine at specified conditions of temperature and pressure. |
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See Figure 10.2. |
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Density of Cl2 Gas |
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32°F, 14.696 psia |
0.2006 lb/ft3 |
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Density of Saturated Cl2 Gas |
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32°F, 53.51 psia |
0.7632lb/ft3 |
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Density of Saturated Cl2 Liquid |
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32°F, 14.696 psia |
91.56 lb/ft3 |
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Latent Heat of Vaporization |
The heat required to evaporate a unit weight of chlorine |
At the normal boiling point |
123.9 Btu/lb |
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Liquid-Gas Volume Relationship |
The weight of one volume of liquid chlorine equals the weight of 456.5 volumes of chlorine gas. |
32°F, 14.696 psia |
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Melting Point (Freezing Point) |
The temperature at which solid chlorine melts or liquid chlorine solidifies |
14.696 psia |
-149.76°F |
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Solubility in Water |
The weight of chlorine which can be dissolved in a given amount of water at a given temperature when the total vapor pressure of chlorine and the water equals a designated value. |
60°F,14.696 psia (15.6°C,101.325 kPa) |
6.93 lbs/100gal |
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Specific Gravity of Cl2 Gas |
The ratio of the density of chlorine gas at standard conditions to the density of air under the same conditions: |
32°F, 14.696 psia |
2.485 |
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Specific Gravity of Cl2 Liquid |
The ratio of the density of saturated liquid chlorine to the density of water at its maximum density - 39°(4°C) |
32°F |
1.467 |
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Specific Heat |
The heat required to raise the temperature of a unit weight of chlorine one degree. |
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Saturated Gas at constant pressure |
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32°F |
0.1244 Btu/lb °F (0.521 kJ/kg K) |
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Saturated Gas at constant volume |
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32°F |
0.08887 Btu/lb °F |
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Saturated Liquid |
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32°F |
0.2264 Btu/lb °F (0.948 kJ/kg K) |
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Ratio for Saturated Gas |
Ratio of gas specific heat at constant pressure to gas specific heat at constant volume |
32°F |
1.400 |
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Specific Volume |
The volume of a unit mass of chlorine at specified conditions of temperature and pressure. |
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Gas |
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32°F, 14.696 psia |
4.986 ft3/lb |
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Saturated Gas |
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32°F |
1.310 ft3/lb |
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Saturated Liquid |
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32°F |
0.01092 ft3/lb (0.0006818 m3/kg) |
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Vapor Pressure |
The absolute pressure of chlorine gas above liquid chlorine when they are in equilibrium |
32°F |
53.51 psia |
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Viscosity |
The measure of internal molecular friction when chlorine molecules are in motion |
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Saturated Gas |
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32°F |
0.0125 cP |
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Liquid |
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32°F |
0.3863 cP |
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Flammability
Chlorine is neither explosive nor flammable. Chlorine will support combustion under certain conditions. Many materials that burn in oxygen (air) atmospheres will also burn in chlorine atmospheres. Many organic chemicals react readily with chlorine, sometimes violently.
Valence
Chlorine usually forms compounds with a valence of -1 but it can combine with a valence of +1, +2, +3, +4, +5, or +7.
Reactions with Water
Chlorine is only slightly soluble in water (0.3% to 0.7%) depending on the water temperature.
Reactions with Metals
The reaction rate of dry chlorine with most metals increases rapidly above a temperature which is characteristic for the metal. Consult CI Pamphlet 6 for detailed information on reactivity with metals.
Reactions with Other Elements
Chlorine unites under specific conditions with most of the elements; these reactions may be extremely rapid. Consult CI Pamphlet 121 for more information.
Reactions with Inorganic Compounds
See CI Pamphlet 21.Reactions with Organic Compounds
Chlorine reacts with many organic compounds to form chlorinated derivatives. Some reactions can be extremely violent, especially those with hydrocarbons, alcohols and ethers. Proper methods must be followed, whether in laboratory or plant, when organic materials are reacted with chlorine.
Physical Properties
Figures below are for pure chlorine.
Taken from Chlorine Basics (Pamphlet 1)
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