Section 1PROPERTIES OF BROMINE
1.1 APPENDIX 1 - PHYSICAL PROPERTIES
Reference Source:- Kirk Othmer Encyclopaedia of Chemical Technology 3rd Edition 1978 (Except where otherwise stated).
Boiling Point: 58.8°C
Freezing Point: -7.25°C
Molecular weight: 159.8
Density of Liquid Bromine (g/ml)
Viscosity, 20°C, Centistokes: 0.31 (1)
Vapour Density (air = 1) at Boiling Point: 5.5 (2)
Vol Coeff of Expansion (20 - 30°C) 0.0011 per °C
Vapour Pressure, mmHg, 20°C: 5.87 (See Figure)
Latent Heat of Vaporisation (Boiling Point) 187 kJ/kg (44.8 cal/g)
Specific Heat of Liquid (25°C): 0.473 Kj/kg/°C (2) (0.113 cal/g/°C; 18.09 cal/mole/°C)
Solubility in water at 20°C: 3.41g/100g
Solubility of water in bromine at 20°C: 34 mg/100g
Entropy, liquid, cal/mole °K, 25°C: 36.4 (1)
Dielectric Constant, 10^5 freq., 25°C: 3.33 (1)
Surface tension, dynes/cm, 58.6°C: 36 (1)
Flash point: none
Fire point: none
Refractive index, 15°C/D: 1.661 (1)
Compressibility, saturated vapours, PV/RT, 25°C: 0.991 (1)
Two physical properties of bromine can be exploited to reduce evolution of fumes from a spillage, namely its density and its limited solubility in water. Laboratory tests carried out by ICI have indicated that evolution of fumes from liquid bromine caught in a water filled bund or contained and covered by a layer of water from a drenching system is suppressed by 99%.
1. Bromine Handling Manual, Albemarle 1995
2. Occupational Health Guidelines for Bromine. US Dept of Labour 1978.
3. Hildebrand et al.; Journal American Chemical Society 80, 4129 (1958).
1.2 CHEMICAL PROPERTIES
Bromine is highly reactive and a strong oxidising agent. It will react vigorously with reducing agents and many organic materials, including solvents. Although bromine is not itself combustible, the heat of reaction is sufficient to initiate combustion when in contact with phosphorus or sulphur. Dry loose flammable material such as paper and wood shavings can be similarly ignited, and liquid bromine will attack some plastics and rubber.
Dry bromine will react violently with aluminium, titanium, mercury and alkali metals apart from sodium, but is not generally reactive with other metals. Reactivity is, however, markedly increased by traces of water or some organic impurities. Relatively few metals are resistant to moist bromine.
Bromine is very hygroscopic. Dry bromine rapidly absorbs water from the atmosphere. It is therefore advisable, except under well defined circumstances, to treat all bromine as being moist.
1.3 VAPOUR PRESSURE/TEMPERATURE - BROMINE
Note: °C = (°F - 32) x 5/9
Source: Bromine Handling Manual, Albemarle Corporation 1995
1.4 APPENDIX 2 - MATERIALS OF CONSTRUCTION FOR USE IN CONTACT WITH BROMINE
The information summarised below provides guidance on the selection of materials of construction. The user should consult a reputable materials supplier and the bromine supplier to satisfy himself that it will give the required performance under the actual conditions of use including temperature, pressure and presence of moisture.
CONDITION OF BROMINE
Dry (Below 30 mg/kg)
|Metals||Lead (2) (3) (4)||S||at 25°C||G||up to 50°C|
|Tantalum (3)||G||up to 200°C||G||up to 200°C|
|Mild Steel, Cast Iron||U||U||U||U|
|Stainless Steels (Austenitic)||U||U||S(5)||S(5)|
|Niobium and Niobium/Tantalum Alloy||S||S||S||S|
|Stoneware, Porcelain, Glass (6)||G||G||G||G|
|PTFE, PCTFE, PVDF, FEP (7)||G||G||G||G|
|G = Good
S = Satisfactory under carefully controlled conditions
U = Unsatisfactory
1. The resistance to wet bromine depends upon the water content and temperature. Bromine in contact with air of 80% relative humidity can pick up 300 mg of water per litre.
2. Chemical Lead, BS 334: 1983 (type A).
3. Data refer to gas or liquid.
4. Tin-free flux should be used for lead burning.
5. Only if found satisfactory after specific trials. Evidence on titanium is conflicting and it should be contemplated for use only with wet bromine gas and then with caution.
6. Upper temperature limit is determined by factors other than corrosion. Avoid mechanical or thermal shock.
7. Notes on the Selection and Use of Fluorocarbon Polymers
Considerable experience has been gained with the use of fluorocarbon polymers, especially polyvinylidene fluoride (PVDF). PVDF lined mild steel pipework and solid PVDF (ie pipework made entirely of PVDF, that is, not a lining) are both commonly available commercially. Both have excellent resistance to wet and dry bromine.
All fluorocarbon polymers are permeable, the degree of permeability progressively increasing from PVDF to PCTFE and to PTFE. Experience has shown that PVDF linings are chemically resistant to wet and dry bromine up to temperatures of 120°C. Considerable stress and distortion occur at higher temperatures and the maximum temperature recommended is 95°C.
The standards of construction for storage tanks and vessels are recommended in 3.4.1. Other vessels which may contain bromine are covered in 3.4.2. In the case of vessels and equipment such as columns, small pots and vapour phase items with capacities of less than 400 kg of bromine, glass reinforced plastic (GRP) construction internally lined with PVDF is often preferable to PVDF lined steel. GRP has a higher coefficient of thermal expansion than steel but it is important to take into consideration that both have a lower coefficient of expansion than PVDF. GRP has an advantage in that it can be laid over the welded lining construction for intricate pieces and also has a good general corrosion resistance in contaminated atmospheres. Provision should be made with lined GRP vessels to enable spark testing of weld points on the lining by the inclusion of conductive resins in the bonding. The GRP construction should comply with BS 4994, 1987.
Where solid PVDF pipework is used it should be of fusion weld construction and jointed with steel backed stub or full face flanges. Socket weld joints are used in sizes up to about 3" ns and butt welds in sizes of 3" ns and above. Severe embrittlement has been reported in both butt and socket welds on certain PVDF polymers. Before using solid PVDF pipework with fusion weld joints the conditions of use should be fully considered and advice sought. In all cases particular attention should be given to specifying and controlling the fabrication methods to be used.
Except over very short distances all pipework should be continuously supported and free from imposed stresses (eg heavy values). Initially most solid PVDF pipework has the advantage of being translucent, but this will be limited in time by permeation of bromine into it. Where BS or Industry Standards have not yet been established the design and construction of plastic pipelines should be strictly in accord with the manufacturers recommendations and installed by competent personnel using suitable equipment approved by the manufacturer. Pipework should be suitably examined and tested before use with bromine.