Azeotrope

An azeotrope is a mix of two liquids that cannot be separated by distillation as the vapor of both liquids comes at the same time. It is sometime possible to separate the liquids anyway by using various techniques, one of them being vacuum distillation to break the azeotrope, another being salting out. However, these do not work in every case.

Binary azeotropes

Data source color code
CRC & Lange's	CRC only	Lange's only	other (see references)

Azeotropes of water, b.p.=100 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav with various alcohols ethanol 78.4 78.1 95.5 0.804 methanol 64.7 No azeotrope n-propanol 97.2 87.7 71.7 0.866 iso-propanol 82.5 80.4 87.9 0.818 n-butanol 117.8 92.4 55.5 U 79.9 L 7.7 U 0.849 L 0.990 sec-butanol 99.5 88.5 67.9 0.863 iso-butanol 108.0 90.0 70.0 U 85.0 L 8.7 U 0.839 L 0.988 tert-butanol 82.8 79.9 88.3 allyl alcohol 97.0 98.2 72.9 0.905 benzyl alcohol 205.2 99.9 9 furfuryl alcohol 169.4 98.5 20 cyclohexanol 161.1 97.8 20 benzyl alcohol 205.4 99.9 9 with various organic acids formic acid 100.8 107.3 77.5 acetic acid ‡ 118.1 No azeotrope propionic acid 141.1 99.98 17.7 1.016 butyric acid 163.5 99.94 18.4 1.007 iso-butyric acid 154.5 99.3 21 with mineral acids nitric acid 86.0 120.5 68 1.405 perchloric acid 110.0 203 71.6 hydrofluoric acid 19.9 120 37 hydrochloric acid –84 110 20.24 1.102 hydrobromic acid –73 126 47.5 1.481 hydroiodic acid –34 127 57 sulfuric acid 290 338 98 with various alkyl halides ethylene chloride 83.7 72 91.8 propylene chloride 96.8 78 89.4 chloroform 61.2 53.3 97.0 U 0.8 L 99.8 U 1.004 L 1.491 carbon tetrachloride 76.8 66.8 95.9 U 0.03 L 99.97 U 1.000 L 1.597 methylene chloride 40.0 38.8 99.6 U 2.0 99.9 U 1.009 L 1.328 with various esters ethyl acetate 77.1 70.4 91.9 U 96.7 L 8.7 U 0.907 L 0.999 methyl acetate 57.0 56.1 95.0 0.940 n-propyl acetate 101.6 82.4 86 ethyl nitrate 87.7 74.4 78 with various other solvents acetone ‡ 56.5 °C No azeotrope methyl ethyl ketone 79.6 73.5 89 0.834 pyridine 115.5 92.6 57 1.010 benzene 80.2 69.3 91.1 U 99.94 L 0.07 U 0.880 L 0.999 toluene 110.8 84.1 79.8 U 99.95 L 0.06 U 0.868 L 1.000 cyclohexane 80.7 69.8 91.5 U 99.99 L 0.01 U 0.780 L 1.00 diethyl ether 34.5 34.2 98.7 0.720 tetrahydrofuran 66 65 95 anisole 153.9 95.5 59.5 acetonitrile 82.0 76.5 83.7 0.818 chloral 97.75 95.0 93.0 hydrazine 113.5 °C 120.3 °C 68.5 ‡ CRC 44th ed. lists azeotropes for acetic acid/water and acetone/water, Lange's 10th ed. as well as numerous web sources indicate no azeotrope for these pairs. Azeotropes of allyl alcohol, b.p.=97.0 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav with various solvents methyl butyrate 102.7 93.8 45 n-propyl acetate 101.6 94.2 47 benzene 80.2 76.8 82.6 0.874 toluene 110.8 92.4 50 cyclohexane 80.8 74 80 carbon tetrachloride 76.8 72.3 88.5 1.450 ethylene chloride 83.7 79.9 82		Azeotropes of ethanol, b.p.=78.4 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav with various esters ethyl acetate 77.1 71.8 69.2 0.863 methyl acetate 57.0 56.9 97 ethyl nitrate 87.7 71.9 56 isopropyl acetate 88.4 76.8 47 with various hydrocarbons benzene 80.2 68.2 67.6 0.848 cyclohexane 80.7 64.9 69.5 toluene 110.8 76.7 32 0.815 n-pentane 36.2 34.3 95 n-hexane 68.9 58.7 79 0.687 n-heptane 98.5 70.9 51 0.729 n-octane 125.6 77.0 22 with various alkyl halides ethylene chloride 83.7 70.5 63 chloroform 61.1 59.4 93 1.403 carbon tetrachloride 76.8 65.1 84.2 1.377 allyl chloride 45.7 44 95 n-propyl chloride 46.7 45.0 93 isopropyl chloride 36.3 35.6 97.2 n-propyl bromide 71.0 62.8 79.5 isopropyl bromide 59.8 55.6 89.5 n-propyl iodide 102.4 75.4 56 isopropyl iodide 89.4 71.5 73 methyl iodide 42.6 41.2 96.8 methylene chloride 40.1 39.85 95.0 ethyl bromide 38.0 37.0 97.0 trichloroethylene 87 70.9 73.0 1.197 trichlorotrifluoroethane (CFC 113) 47.7 43.8 96.2 1.517 tetrachloroethylene 121.0 76.75 37.0 with various other solvents methyl ethyl ketone 79.6 74.8 60 0.802 acetonitrile 82.0 72.9 43.0 0.788 nitromethane 101.3 75.95 26.8 tetrahydrofuran P = 100 kPa 65.6 65.4 3.3 thiophene 84.1 70.0 55.0 carbon disulfide 46.2 42.4 92
		Azeotropes of methanol, b.p.=64.7 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav with various esters methyl acetate 57.0 53.8 81.3 0.908 ethyl acetate 77.1 62.3 56 0.846 ethyl formate 54.1 51.0 84 with various hydrocarbons benzene 80.2 58.3 60.4 0.844 toluene 110.8 63.8 31 0.813 cyclohexane 80.8 54.2 62.8 U 97.0 L 39.0 n-pentane 36.2 30.8 91 n-hexane 68.9 50.6 72 n-heptane 98.5 59.1 48.5 n-octane 125.8 63.0 72.0 with various alkyl halides ethylene chloride 83.7 61.0 68 chloroform 61.1 53.5 87.4 1.342 carbon tetrachloride 76.8 55.7 79.4 1.322 ethyl bromide 38.4 35.0 95.5 n-propyl chloride 46.6 40.5 90.5 isopropyl chloride 36.4 33.4 94 n-propyl bromide 71.0 54.5 79 isopropyl bromide 59.8 48.6 85.0 isopropyl iodide 89.4 61.0 62 trichloroethylene 87.2 60.2 64 tetrachloroethylene 121.1 63.5 40.6 trichlorotrifluoroethane (CFC 113) 47.7 39.9 94 with various other solvents nitromethane 101.2 64.6 9 acetone 56.5 55.7 87.9 0.796 acetonitrile 82.0 63.45 19.0 carbon disulfide 46.2 37.7 86.0 U 50.8 L 97.2 U 0.979 L 1.261 isopropanol 82.5 64.0 20 tetrahydrofuran P = 984 mBar 65.6 60.7 69.0

Azeotropes of n-propanol, b.p.=97.2 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav with various solvents methyl butyrate 102.7 94.4 51 n-propyl formate 80.8 80.65 97 n-propyl acetate 101.6 94.7 49 0.833 benzene 80.2 77.1 83.1 toluene 110.8 92.4 47.5 0.836 n-hexane 68.9 65.7 96 carbon tetrachloride 76.8 73.1 88.5 1.437 ethylene chloride 83.7 80.7 81 n-propyl bromide 71.0 69.7 91 Azeotropes of acetic acid, b.p.=118.5 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav with various solvents benzene 80.2 80.05 98 0.882 cyclohexane 80.8 79.7 98 toluene 110.8 105.0 72 0.905 m-xylene 139.0 115.4 27.5 0.908 n-heptane 98.5 92.3 70 n-octane 125.8 109.0 50 isopropyl iodide 89.2 88.3 91 carbon tetrachloride 76.8 76.6 97 tetrachloroethylene 121.0 107.4 61.5 ethylene bromide 131.7 114.4 45 1,1-dibromoethane 109.5 103.7 75.0 methylene bromide 98.2 94.8 84.0 pyridine 115.3 139.7 65.0 1.024

Azeotropes of isopropanol, b.p.=82.5 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav with various esters ethyl acetate 77.1 75.3 75 0.869 isopropyl acetate 91.0 81.3 40 0.822 with various hydrocarbons benzene 80.2 71.9 66.7 0.838 toluene ‡ 110.8 80.6 42 cyclohexane 81.0 68.6 67.0 0.777 n-pentane 36.2 35.5 94 n-hexane 68.9 62.7 77 n-heptane 98.5 76.3 46 with various alkyl halides carbon tetrachloride 76.8 69.0 82 1.344 chloroform 61.1 60.8 95.8 ethylene chloride 83.7 74.7 56.5 ethyl iodide 83.7 67.1 85 n-propyl chloride 46.7 46.4 97.2 n-propyl bromide 71.0 66.8 79.5 isopropyl bromide 59.8 57.8 88 n-propyl iodide 102.4 79.8 58 isopropyl iodide 89.4 76.0 68 tetrachloroethylene 121.1 81.7 19.0 with various other solvents methyl ethyl ketone 79.0 77.5 68 0.800 diisopropyl ether 69 66.2 85.9 nitromethane 101.0 79.3 70 ‡ CRC and Lange's disagree on this azeotrope, but web source corroborates CRC

Azeotropes of formic acid, b.p.=100.8 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav with various hydrocarbons benzene 80.2 71.7 69 toluene 110.8 85.8 50 m-xylene 139.0 94.2 29.8 n-pentane 36.2 34.2 90 n-hexane 68.9 60.6 72 n-heptane 98.5 78.2 56.5 n-octane 125.8 90.5 37 with various alkyl halides chloroform 61.2 59.2 85 carbon tetrachloride 76.8 66.7 81.5 methyl iodide 42.6 42.1 94 ethyl bromide 38.4 38.2 97 ethylene chloride 83.6 77.4 86 ethylene bromide 131.7 94.7 48.5 n-propyl chloride 46.7 45.6 92 isopropyl chloride 34.8 34.7 98.5 n-propyl bromide 71.0 64.7 73 isopropyl bromide 59.4 56.0 86 with various other solvents carbon disulfide 46.3 42.6 83 Azeotropes of benzene, b.p.=80.1 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav cyclohexane 81.4 77.8 45.0 0.834 ethyl nitrate 88.7 80.03 12.0 methyl ethyl ketone 79.6 78.4 37.5 0.853 nitromethane 101.0 79.15 14.0 acetonitrile 82.0 73.0 34.0 n-heptane 98.5 80.0 1

Azeotropes of ethylene glycol, b.p.=197.4 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav with various solvents ethyl benzoate 212.6 186.1 53.5 diphenyl 254.9 192.0 36 mesitylene 164.6 156.0 87 naphthalene 218.1 183.9 49 toluene 110.8 110.2 93.5 m-xylene 139.0 135.6 85 o-xylene 144.4 139.6 84.0 ethylene bromide 131.7 129.8 96 nitrobenzene 210.9 185.9 41 chlorobenzene 132.0 130.1 5.6 benzyl chloride 179.3 167.0 70 benzyl alcohol 205.1 193.1 44 anisole 153.9 150.5 89.5 acetophenone 202.1 185.7 48 aniline 184.4 180.6 76 o-cresol 191.1 189.6 73 Azeotropes of glycerol, b.p.=291.0 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav diphenyl 254.9 243.8 45 naphthalene 218.1 215.2 90 Azeotropes of acetone, b.p.=56.5 °C 2nd Component b.p. of comp. (˚C) b.p. of mixture (˚C)  % by weight spef. grav carbon disulfide 46.3 39.3 67.0 1.04 chloroform 61.2 64.7 80.0 1.268 cyclohexane 81.4 53.0 33.0 n-hexane 68.8 49.8 41 ethyl iodide 56.5 55.0 40.0 carbon tetrachloride 76.8 56.2 11.9

Miscellaneous azeotrope pairs component 1 b.p. comp. 1 (˚C) component 2 b.p. comp. 2 (˚C)   b.p. azeo. (˚C)  % wt comp. 1  % wt comp. 2 spec. grav. acetaldehyde 21.0 diethyl ether 34.6 20.5 76.0 24.0 0.762 n-butane –0.5 –7.0 16.0 84.0 acetamide 222.0 benzaldehyde 179.5 178.6 6.5 93.5 nitrobenzene 210.9 202.0 24.0 76.0 o-xylene 144.1 142.6 11.0 89.0 acetonitrile 82.0 ethyl acetate 77.15 74.8 23.0 77.0 toluene 110.6 81.1 25.0 75.0 acetylene –86.6 ethane –88.3 –94.5 40.7 59.3 aniline 184.4 o-cresol 191.5 191.3 8.0 92.0 carbon disulfide 46.2 diethyl ether 34.6 34.4 1.0 99.0 0.719 1,1-dichloroethane 57.2 46.0 94.0 6.0 methyl ethyl ketone 79.6 45.9 84.7 15.3 1.157 ethyl acetate 77.1 46.1 97 3 methyl acetate 57.0 40.2 73 27 chloroform 61.2 methyl ethyl ketone 79.6 79.9 17.0 83.0 0.877 n-hexane 68.7 60.0 72.0 28.0 1.101 carbon tetrachloride 76.8 methyl ethyl ketone 79.9 73.8 71.0 29.0 1.247 ethylene dichloride 84.0 75.3 78.0 22.0 1.500 ethyl acetate 77.1 74.8 57.0 43.0 1.202 cyclohexane 81.4 ethyl acetate 77.15 72.8 46.0 54.0 ethyl nitrate 88.7 74.5 64.0 36.0 diethyl ether 34.6 methyl formate 31.50 28.2 44.0 56.0 methylene chloride 40 40.8 30 70 nitromethane 101.0 toluene 110.8 96.5 55.0 45.0 tetrahydrofuran 65.6 chloroform 61.2 72.5 34.5 65.5 n-hexane 69 63.0 46.5 53.5 toluene 110.63 pyridine 115.3 110.2 78.0 22.0 propylene glycol 188.2 aniline 184.4 179.5 43 57 o-xylene 144.4 135.8 10 90 toluene 110.6 110.5 1.5 98.5

References

• http://vle-calc.com/azeotrope.html