Chemical Properties

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.

Atomic and Molecular Properties

Atomic Symbol - Cl

Atomic Weight - 35.453

Atomic Number - 17

Molecular Weight of Cl2 - 70.906

Chemical Properties

Physical Properties

Property

Definition

Conditions

Value

Boiling Point
(Liquefying Point)

The temperature at which liquid chlorine vaporizes

14.696 psia
(101.325 kPa)

-29.15°F
(-33.97°C)

Critical Density

The mass of a unit volume of chlorine at the critical pressure and temperature

35.77 lb/ft3
(573.0 kg/m3)

Critical Pressure

The vapor pressure of liquid chloride at the critical temperature

1157.0 psia
(7977 kPa)

Critical Temperature

The temperature above which chlorine exists only as a gas no matter how great the pressure

290.75°F
(143.75°C)

Critical Volume

The volume of a unit mass of chlorine at the critical pressure and temperature

0.02795 ft3/lb
(0.001745 m3/kg)

Density

The mass of a unit volume of chlorine at specified conditions of temperature and pressure.

See Figure 10.2.

Density of Cl2 Gas

32°F, 14.696 psia
(0°C, 101.325 kPa)

0.2006 lb/ft3
(3.213 kg/m3)

Density of Saturated Cl2 Gas

32°F, 53.51 psia
(0°C, 368.9 kPa)

0.7632lb/ft3
(12.23 kg/m3)

Density of Saturated Cl2 Liquid

32°F, 14.696 psia
(0°C, 101.325 kPa)

60°F, 86.58 psia

(15.6°C, 597.0 kPa)

91.56 lb/ft3
(1467 kg/m3)

88.76 lb/ft3
11.87 lb/gal
(1422 kg/m3)

Latent Heat of Vaporization

The heat required to evaporate a unit weight of chlorine

At the normal boiling point

123.9 Btu/lb
(288.1 kJ/kg)

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
(0°C, 101.325 kPa)

Melting Point (Freezing Point)

The temperature at which solid chlorine melts or liquid chlorine solidifies

14.696 psia
(101.325 kPa)

-149.76°F
(-100.98°C)

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
(8.30 kg/m3)
See
Figure 10.3

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
(0°C, 101.325 kPa)

2.485
(Note: The density of air, free of moisture at the same conditions is 1.2929 kg/m3)

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
(0°C)

1.467

Specific Heat

The heat required to raise the temperature of a unit weight of chlorine one degree.

Saturated Gas at constant pressure

32°F
(0°C)
77°F
(25°C)

0.1244 Btu/lb °F (0.521 kJ/kg K)
0.1347 Btu/lb
°F (0.564 kJ/kg K)

Saturated Gas at constant volume

32°F
(0°C)
77°F
(25°C)

0.08887 Btu/lb °F
(0.372 kJ/kg
K)
0.09303 Btu/lb
°F (0.3895 kJ/kg K)

Saturated Liquid

32°F
(0°C)
77°F
(25°C)

0.2264 Btu/lb °F (0.948 kJ/kg K)
0.2329 Btu/lb
°F (0.975 kJ/kg K)

Ratio for Saturated Gas

Ratio of gas specific heat at constant pressure to gas specific heat at constant volume

32°F
(0°C)
77°F
(25°C)

1.400

1.448

Specific Volume

The volume of a unit mass of chlorine at specified conditions of temperature and pressure.

Gas

32°F, 14.696 psia
(0°C, 101.325 kPa)

4.986 ft3/lb
(0.3113 m3/kg).

Saturated Gas

32°F
(0°C)

1.310 ft3/lb
(0.08179 m3/kg).

Saturated Liquid

32°F
(0°C)

0.01092 ft3/lb (0.0006818 m3/kg)

Vapor Pressure

The absolute pressure of chlorine gas above liquid chlorine when they are in equilibrium

32°F
(0°C)
77°F
(25°C)

53.51 psia
(368.9 kPa)
112.95 psia
(778.8 kPa)

Viscosity

The measure of internal molecular friction when chlorine molecules are in motion

Saturated Gas

32°F
(0°C)
60°F
(15.6°C)

0.0125 cP
(0.0125 mPa
s)
0.0132 cP
(0.0132 mPa
s)

Liquid

32°F
(0°C)
60°F
(15.6°C)

0.3863 cP
(0.3863 mPa
s)
0.3538 cP
(0.3538 mPa
s)

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. An important specific compound of concern is hydrogen. Chlorine reacts explosively with hydrogen in a range of 4% to 93% hydrogen. The reaction is initiated very easily much the same way as hydrogen and oxygen. See Pamphlet 121 for more information.

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.

Chemical Reactions

Reactions with Water

Chlorine is only slightly soluble in water (0.3% to 0.7%) depending on the water temperature. However the resulting water phase is extremely corrosive, see Reactions with Metals below.

Reactions with Metals

The reaction rate of dry chlorine with most metals increases rapidly above a temperature which is characteristic for the metal. Two of the more common metals are titanium and steel. In the presence of dry chlorine, titanium is flammable. Care should be taken to make sure titanium materials are not used in dry chlorine service. Steel is the most common material used in dry chlorine service. At temperatures above 300°F (149°C) a chlorine/steel fire can result. It is important to make sure steel in chlorine service does not go above this temperature either through internal/external heating or mechanical abrasion. Moist chlorine, primarily because of the hydrochloric and hypochlorous acids formed through hydrolysis, is very corrosive to most common metals. Platinum, silver, tantalum and titanium are resistant. Consult CI Pamphlet 6 (11.1) for detailed information on reactivity with metals.

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

See CI Pamphlet 1.

Taken from Chlorine Basics (Pamphlet 1)