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

  1. Typical DMSO Properties
  2. Vapor Pressure vs. Temperature Curve for DMSO
  3. Specific Gravity of DMSO as a Function of Temperature
  4. DMSO Viscosity as a Function of Temperature
  5. Initial Sorption Rates of DMSO at Various Relative Humidities
  6. Hygroscopocities of DMSO at Various Relative Humidities
  7. Freezing Temperatures for DMSO – Water Solutions
  8. Freezing Point Data for DMSO – Water Solutions
  9. Vapor – Liquid Equilibrium for DMSO – Water Solutions
  10. Heat Capacity and Density of DMSO
  11. Boiling Point/Temperature Curves: DMSO – Water Solutions
  12. Heat of Mixing, DMSO – Water mixtures, 32°C
  13. Specific Gravity of DMSO – Water Solutions
  14. Viscosity of DMSO – Water Solutions
  15. Chemical and Thermal Stability of DMSO
  16. 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

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