English Request a Sample 800.426.6620 SEARCH MENU DMSO Physical Properties Introduction to DMSO Physical Properties Dimethyl Sulfoxide (DMSO) is a highly polar and water miscible organic liquid. It is essentially odorless, and has a low level of toxicity. DMSO is a dipolar aprotic solvent, and has a relatively high boiling point. Further below is a compilation of Physical Properties data for this useful solvent. CONTENTS Typical DMSO Properties Vapor Pressure vs. Temperature Curve for DMSO Specific Gravity of DMSO as a Function of Temperature DMSO Viscosity as a Function of Temperature Initial Sorption Rates of DMSO at Various Relative Humidities Hygroscopocities of DMSO at Various Relative Humidities Freezing Temperatures for DMSO – Water Solutions Freezing Point Data for DMSO – Water Solutions Vapor – Liquid Equilibrium for DMSO – Water Solutions Heat Capacity and Density of DMSO Boiling Point/Temperature Curves: DMSO – Water Solutions Heat of Mixing, DMSO – Water mixtures, 32°C Specific Gravity of DMSO – Water Solutions Viscosity of DMSO – Water Solutions Chemical and Thermal Stability of DMSO Comparative Viscosities and Evaporation Times of Common Solvents Figure 1 TYPICAL DMSO PROPERTIES (IN ALPHABETICAL ORDER) Parameter Value Auto ignition temp, in air 300-302°C (572-575°) Boiling point (1 atmosphere) 189°C (372°F) Coefficient of expansion 0.00088/°C Conductivity (Electrical), 20°C 3×10-8 (ohm-1 cm-1) 3 x 10-8 (ohm-1 cm-1) @ 80°C 7 x 10-8 (ohm-1 cm-1) Critical heat flux (4.10×105 J / s / m2) 1.3 x 105 Btu/hr x ft-2 Critical molar volume 2.38 x 10-4 m3 Critical Pressure 56.3 atm. abs. Critical temperature 447°C (837°F) Density, at 25°C (see Figure 3) 1.0955 g / cm3 Dielectric constant, 1 MHz, @ 20°C 48.9 @ 40°C 45.5 Diffusion coefficient 9.0 x 104 cm2 / sec. Dipole moment, D 4.3 Evaporation rate index @ 25°C Relative to n-butyl acetate 0.026 Relative to diethyl ether 0.0005 Flammability limits in air lower (100°C) 3 – 3.5% by volume upper 42 – 63% by volume Flash point (open cup) 95°C (203°F) Flash point (closed cup) 89°C (192°F) Freezing point 18.55°C (65.4°F) Heat capacity, ideal gas, Cp(T°K) -0.227×10-4T2 6.94+5.6×10-2T Heat capacity (liq.), 25°C 0.47 cal / g / °C Heat of combustion 6054 cal / g Heat of fusion 41.3 cal / g Heat of solution in water at 25°C -54 cal/g Heat of vaporization at 70°C 11.3 kcal/mol Henry’s constant @ 21°C 991000 Molar freezing point constant 4.07°C / mol Molar volume 71.2 cm3 / g Molecular weight 78.13 pKa 35.1 pK BH+ -2.7 Refractive index ND@25°C 1.4768 Solubility parameters Hansen’s – Dispersion 9.0 (cal / cm3)1/2 – Polar 8.0 (ca l / cm3)1/2 – Hydrogen bonding 5.0 (cal / cm3)1/2 Hildebrand’s 13.0 (cal / cm3)1/2 Specific heat at 29.5°C 0.47± 0.015 cal /g /°C Surface tension at 20°C 43.53 dynes / cm Vapor pressure at 25°C (See Figure 1) 0.600 mm Hg Viscosity, cP, at 25°C (See Figure 4) 2.0 Log octanol-water partition coefficient -1.35 Figure2 VAPOR PRESSURE VS. TEMPERATURE CURVE FOR DMSO Figure 3 SPECIFIC GRAVITY OF DMSO AS A FUNCTION OF TEMPERATURE Temperature (°C) Specific Gravity (g/cm³) 15.6 1.1047 21 1.0993 25 1.0955 30 1.0904 40 1.0803 50 1.0702 75 1.0454 100 1.0200 125 0.9946 150 0.974 Figure 4 DMSO VISCOSITY AS A FUNCTION OF TEMPERATURE Temperature (°C) Viscosity (cP) 25 1.991 30 1.808 40 1.511 50 1.286 75 0.916 100 0.691 125 0.546 Figure 5 INITIAL SORPTION RATES OF DMSO AT VARIOUS RELATIVE HUMIDITIES AT 22°C Figure 6 HYGROSCOPICITIES OF DMSO AT VARIOUS RELATIVE HUMIDITIES AT 22°C Figure 7 FREEZING TEMPERATURE FOR DMSO-SOLVENT MIXTURES Figure 8 FREEZING POINT DATA FOR DMSO WATER SOLUTIONS FREEZING POINT DATA FOR DMSO WATER SOLUTIONS Figure 9 Figure 10 Figure 11 VAPOR-LIQUID EQUILIBRIUM FOR DMSO-WATER SOLUTIONS (ONE ATMOSPHERE PRESSURE) Figure 12 HEAT CAPACITY AND DENSITY OF DMSO Temperature, °C Cp (liquid), cal/(g)/(°C) Density, grams/cc 30 0.47 1.096 60 0.47 1.062 100 0.48 1.023 150 0.52 0.974 Figure 13 VAPOR-LIQUID EQUILIBRIUM FOR DMSO-WATER SOLUTIONS (ONE ATMOSPHERE PRESSURE) Temperature, °C Mol Fraction Water in Liquid Mol Fraction Water in Vapor 100.0 1.000 1.000 100.6 0.988 0.9998 101.0 0.975 0.9997 102.0 0.945 0.9994 103.3 0.909 0.9989 105.0 0.865 0.9983 108.0 0.810 0.997 113.0 0.740 0.994 118.0 0.675 0.990 120.0 0.645 0.986 130.0 0.513 0.964 143.0 0.378 0.921 149.0 0.313 0.890 165.0 0.176 0.773 174.5 0.100 0.628 177.0 0.081 0.573 183.0 0.046 0.353 184.6 0.034 0.282 187.7 0.011 0.100 189.0 0.000 0.000 Figure 14 BOILING POINT/ TEMPERATURE CURVES: DMSO WATER SOLUTIONS (ONE ATMOSPHERE PRESSURE) Figure 15 HEAT OF MIXING OF DMSO – H20 SYSTEM AT 32°C Figure 16 SPECIFIC GRAVITY OF DMSO WATER SOLUTIONS Figure 17 VISCOSITY OF DMSO WATER SOLUTIONS Chemical and Thermal Stability of DMSO DMSO is highly stable at temperatures below 150°C. For example, holding DMSO at 150°C for 24 hours, one could expect a loss of between 0.1 and 1.0%. Retention times even in batch stills are usually considerably less than this, and therefore, losses would be correspondingly less. It has been reported that only 3.7% of volatile materials are produced during 72 hours at the boiling point (189°C) of DMSO. Slightly more decomposition, however, can be expected with the industrial grade material. Thus, about 5% DMSO decomposes at reflux after 24 hours. Al- most half of the weight of the volatile materials is paraformaldehyde. Dimethyl sulfide, di- methyl disulfide, bis-(methylthio)methane and water are other volatile products. A small amount of dimethyl sulfone can also be found. The following sequence of reactions explains the formation of these decomposition products: DMSO is remarkably stable in the presence of most neutral or basic salts and bases. When samples of DMSO (300g) are refluxed for 24 hours with 100g each of sodium hydroxide, sodium carbonate, sodium chloride, sodium cyanide, sodium acetate and sodium sulfate, little or no decomposition takes place in most cases. The results are shown in Figure 18. Figure 18 RESULTS OF REFLUX WITH DMSO AND VARIOUS MATERIALS (24 HOURS) Compound (100g) in 300g DMSO Reflux Temp. (°C) DMSO Recovered % of Original % Decomposition Products DMS(a) DMDS(b) BMTM(c) HCHO(d) MM(e) NaOH 185-140(f) 93.7 63 31 – – – Na₂CO₃ 190 96.3 – 14 – – – NaCl 190 98.7 – 15 – – – NaCN 148-164(g) 100.0 – – – – – NaOAc 182-187 97.0 22 33 8 20 – Na₂SO4 181-148(h) 85.4 – – – – – DMSO Only 189 98.0 15 30 30 – – (a) Dimethyl sulfide (b) Dimethyl Disulfide (c) Bis-(methylthio)methane (d) Methyl mercaptan (e) Formaldehyde (f) Reflux temperature decreased from 185°C to 140°C over the first 16 hours (g) Reflux temperature was 148°C for 20 hours; increased to 164°C during the last 4 hours (h) Reflux temperature decreased gradually from 181°C to 148°C Figure 19 THERMAL STABILITY OF DMSO DMSO does not seem to be hydrolyzed by water and very little decomposition of DMSO takes place when it is heated under reflux for periods of 5 to 16 hours. The following tests, shown in Figure 20, have been performed: 1) 10 parts DMSO + 1 part water, 2) 60 parts DMSO + 5 parts water + 1 part sodium hydroxide, 3) 60 parts DMSO + 12 parts water + 1 part sodium bicarbonate, 4) DMSO alone. Figure 20 REFLUXING OF DMSO AND MIXTURES, FOR SHORTER PERIODS Composition of Sample Parts Reflux Temp.(°C) Time(hr) Organic Products Composition, % DMSO DMS DMDS BMTM 10 DMSO: 1 H₂O 152 515 10099.7 00.15 00 00.15 60 DMSO: 5H₂O:1 NaOH 155 58 99.899.3 0.10.6 0.10.1 00 60 DMSO: 12 H₂O: 1 NaHCO₃ 131 612 99.999.8 0.10.2 00 00 DMSO Only 191 59 16 99.899.1 99.0 0.10.2 0.2 0.10.2 0.2 00.5 0.6 DMSO is also stable in the presence of concentrated sulfuric or hydrochloric acid at 100°C for up to 120 minutes of heating at atmospheric pressure. Phosphoric acid causes more rapid decomposition of DMSO than does sulfuric or hydrochloric acid. Detected decomposition products are dimethyl sulfide, dimethyl disulfide, and, in smaller quantity, formaldehyde. The results are shown in Figure 21: Figure 21 EFFECT OF HEATING DMSO WITH CONCENTRATED ACIDS Acid Conc. Temp.(°C) Time(min.) DMSO% left % of decomposition product DMS(a) DMDS(b) HCHO(c) H₂SO4 36% 100 1530 120 9999 98 100100 100 H₂SO4 36% 125 15150 210 8686 80 77 10 9393 90 H₃PO4 85% 100 1530 45 60 120 150 9289 89 87 87 86 2545 45 46 46 50 7555 55 54 54 50 Some H₃PO4 85% 125 1560 150 8482 82 2533 33 7567 67 Figure 22 THERMAL DECOMPOSITION OF DMSO Figure 23 COMPARATIVE VISCOSITIES OF COMMON SOLVENTS Solvent Viscosity, cps at 25° Dimethyl Sulfoxide (DMSO) 2.0 Dimethylformamide (DMF) 0.8 N-Methyl-2-pyrrolidone (NMP) 1.6 Butyrolactone 1.7 Cyclohexanone 2.1 Isophorone 2.5 Diacetone alcohol 3.0 Propylene Carbonate 4.0 Sulfolane 10.3 at 30° Figure 24 COMPARATIVE EVAPORATION TIMES FOR COMMON ORGANIC SOLVENTS Solvent 90% Evaporation Times, seconds Dimethyl Sulfoxide (DMSO) 17,600 Dimethylformamide (DMF) 1,570 N-Methyl-2-pyrrolidone (NMP) 2,280 Butyrolactone 3,840 Cyclohexanone 15,400 Isophorone 20,000 Diacetone alcohol 23,700 Propylene Carbonate 119,660 Sulfolane >1,000,000 The information in this bulletin is based on information available to us and on our observations and experiences. 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