How do I compare solvent polarity — polarity index or dielectric constant?

The dielectric constant ε is a bulk physical property describing how well a solvent separates charges and dissolves ions (water 78.4, DMSO 46.7, methanol 32.7, hexane 1.89). Snyder’s polarity index P′ is derived from solubility behaviour and matches what chemists mean by polarity in chromatography and extraction (water 10.2, acetonitrile 5.8, ethyl acetate 4.4, dichloromethane 3.1, hexane 0.1). They mostly agree but not always: chloroform has ε = 4.81 yet P′ = 4.1, and 1,4-dioxane has ε = 2.21 but P′ = 4.8.

Which organic solvents form the bottom layer with water?

Solvents denser than water sink: mainly the halogenated ones — dichloromethane 1.326, chloroform 1.489, carbon tetrachloride 1.594 and 1,2-dichloroethane 1.253 g/mL. Diethyl ether (0.713), ethyl acetate (0.902), hexane (0.655) and toluene (0.867) are lighter and float. Concentrated salt solutions or heavily loaded organic layers can shift this, so if in doubt add a few drops of water and watch which layer they join.

How can I tell whether two solvents are miscible?

Most organic solvents mix with each other. The exceptions involve very polar solvents and alkanes: methanol, acetonitrile, DMF and DMSO do not mix with hexane and other alkanes, and water is immiscible with alkanes, aromatics and halogenated solvents, and only partially miscible with ether, ethyl acetate, 1-butanol and 2-butanone. The matrix follows standard solvent miscibility charts; pairs without reliable data are marked “?” and should be tested.

How do I estimate the polarity of a TLC or HPLC solvent mixture?

Take the volume-weighted average of Snyder’s polarity index: P′ = φA·P′A + φB·P′B. Hexane–ethyl acetate 7:3 gives 0.7×0.1 + 0.3×4.4 = 1.39 and 1:1 gives 2.25. On silica you can also compare the solvent strength ε° (pentane 0, toluene about 0.22, dichloromethane about 0.32, ethyl acetate about 0.48, methanol about 0.73). This is only a rough guide — the actual Rf also depends on selectivity, so run a test plate.

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🧪Common Solvent Properties Table - Boiling Point, Density, Polarity Index and Miscibility Chart

A searchable, sortable reference of 36 common laboratory solvents: water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, 2-butanone, acetonitrile, DMF, DMSO, THF, 1,4-dioxane, diethyl ether, MTBE, ethyl acetate, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, benzene, toluene, o- and p-xylene, hexane, heptane, cyclohexane, pentane, petroleum ether, acetic acid, pyridine, triethylamine, nitromethane, formamide, ethylene glycol and glycerol. For each it lists molar mass, boiling and melting point, density (with its temperature), refractive index nD20, dielectric constant ε, dipole moment, Snyder polarity index P′, water solubility, flash point and the main hazards (flammable, toxic, carcinogen, peroxide former). Values come from the CRC Handbook and standard solvent tables; anything uncertain is left blank rather than guessed. For example water boils at 100 °C with ε = 78.4 at 25 °C; dichloromethane has a density of 1.326 g/mL and forms the bottom layer in an extraction, while diethyl ether (0.713) and hexane (0.655) float on top. Beyond the table you can plot any two properties against each other (such as ε vs boiling point), look up a 36 × 36 miscibility matrix (miscible, partially miscible, immiscible, uncertain), filter for a suitable solvent by boiling range, polarity range, immiscibility with water, density above or below water and safety, see the eluotropic series on silica (ε°), and compute the volume-weighted polarity index of a two-solvent mobile phase: hexane–ethyl acetate 7:3 gives P′ = 0.7×0.1 + 0.3×4.4 = 1.39, and the tool also solves for the ratio that hits a target P′.

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How to use Common Solvent Properties

1Search the property table by name, abbreviation or formula, filter by class and click any header to sort
2Switch to the scatter plot, miscibility matrix or solvent picker and set the properties or filters you need
3Under Eluotropic & mixtures pick two solvents and a ratio to get the mixture’s polarity index, and copy the working

FAQ

How do I compare solvent polarity — polarity index or dielectric constant?: The dielectric constant ε is a bulk physical property describing how well a solvent separates charges and dissolves ions (water 78.4, DMSO 46.7, methanol 32.7, hexane 1.89). Snyder’s polarity index P′ is derived from solubility behaviour and matches what chemists mean by polarity in chromatography and extraction (water 10.2, acetonitrile 5.8, ethyl acetate 4.4, dichloromethane 3.1, hexane 0.1). They mostly agree but not always: chloroform has ε = 4.81 yet P′ = 4.1, and 1,4-dioxane has ε = 2.21 but P′ = 4.8.
Which organic solvents form the bottom layer with water?: Solvents denser than water sink: mainly the halogenated ones — dichloromethane 1.326, chloroform 1.489, carbon tetrachloride 1.594 and 1,2-dichloroethane 1.253 g/mL. Diethyl ether (0.713), ethyl acetate (0.902), hexane (0.655) and toluene (0.867) are lighter and float. Concentrated salt solutions or heavily loaded organic layers can shift this, so if in doubt add a few drops of water and watch which layer they join.
How can I tell whether two solvents are miscible?: Most organic solvents mix with each other. The exceptions involve very polar solvents and alkanes: methanol, acetonitrile, DMF and DMSO do not mix with hexane and other alkanes, and water is immiscible with alkanes, aromatics and halogenated solvents, and only partially miscible with ether, ethyl acetate, 1-butanol and 2-butanone. The matrix follows standard solvent miscibility charts; pairs without reliable data are marked “?” and should be tested.
How do I estimate the polarity of a TLC or HPLC solvent mixture?: Take the volume-weighted average of Snyder’s polarity index: P′ = φA·P′A + φB·P′B. Hexane–ethyl acetate 7:3 gives 0.7×0.1 + 0.3×4.4 = 1.39 and 1:1 gives 2.25. On silica you can also compare the solvent strength ε° (pentane 0, toluene about 0.22, dichloromethane about 0.32, ethyl acetate about 0.48, methanol about 0.73). This is only a rough guide — the actual Rf also depends on selectivity, so run a test plate.

Features

36 common solvents with names, abbreviations and formulas
Boiling point, melting point, density, refractive index, dielectric constant, dipole moment, Snyder P′, flash point
Water solubility plus flammable, toxic, carcinogen and peroxide-former flags
Scatter plot of any two properties, with log axes
Pairwise solvent miscibility matrix and single-pair lookup
Solvent picker by boiling range, polarity, water immiscibility, density and safety
Eluotropic series on silica and mixed-solvent polarity index calculator
Copy the whole table as TSV for Excel

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