This page provides supplementary chemical data on formic acid.

Material Safety Data Sheet

The handling of this chemical may incur notable safety precautions. It is highly recommend that you seek the Material Safety Datasheet (MSDS) for this chemical from a reliable source and follow its directions.

  • in the SDSdata.org database

Structure and properties

Structure and properties
Index of refraction, nD1.3714 at 20 °C
Abbe number?
Dielectric constant, εr58.5 ε0 at 16 °C measured at 400 MHz
Bond strength?
Bond lengthC=O bond: 123 pm C–OH bond: 136 pm
Bond angle?
Magnetic susceptibility?
Surface tension37.67 dyn/cm at 20 °C
Viscosity2.2469 mPa·s at 10 °C 1.7844 mPa·s at 20 °C 1.2190 mPa·s at 40 °C 0.5492 mPa·s at 100 °C
2.2469 mPa·sat 10 °C
1.7844 mPa·sat 20 °C
1.2190 mPa·sat 40 °C
0.5492 mPa·sat 100 °C

Thermodynamic properties

Phase behavior
Triple point281.40 K (8.25 °C), 2.2 kPa
Critical point588 K (315 °C), 5.81 MPa
Std enthalpy change of fusion, ΔfusHo+12.68 kJ/mol
Std entropy change of fusion, ΔfusSo+45.05 J/(mol·K) at 8.25 °C
Std enthalpy change of vaporization, ΔvapHo+23.1 kJ/mol
Std entropy change of vaporization, ΔvapSo+61.8 J/(mol·K)
Solid properties
Std enthalpy change of formation, ΔfHosolid? kJ/mol
Standard molar entropy, Sosolid? J/(mol K)
Heat capacity, cp74.5 J/(mol K) at –22 °C 82.8 J/(mol K) at 0 °C
Liquid properties
Std enthalpy change of formation, ΔfHoliquid–425.5 kJ/mol
Standard molar entropy, Soliquid129.0 J/(mol K)
Enthalpy of combustion, ΔcHo–254.6 kJ/mol
Heat capacity, cp101.3 J/(mol K) at 20–100 °C
Gas properties
Std enthalpy change of formation, ΔfHogas–362.6 kJ/mol
Standard molar entropy, Sogas251.0 J/(mol K)
Heat capacity, cp45.68 J/(mol K) at 25 °C

Vapor pressure of liquid

P in mm Hg11040100400760
T in °C–20.0(s)2.1(s)24.043.880.3100.6

Table data obtained from CRC Handbook of Chemistry and Physics, 44th ed. The "(s)" notation indicates temperature of solid/vapor equilibrium. Otherwise the data is temperature of liquid/vapor equilibrium.

log10 of formic acid vapor pressure. Uses formula: log 10 ⁡ P m m H g = 6.94459 − 1295.26 218.0 + T {\displaystyle \scriptstyle \log _{10}P_{mmHg}=6.94459-{\frac {1295.26}{218.0+T}}} obtained from Lange's Handbook of Chemistry, 10th ed.

Distillation data

BP Temp. °C% by mole water
Vapor-liquid Equilibrium for Formic acid/Water P = 760 mmHg
liquidvapor
102.34.052.45
104.615.510.2
105.921.816.2
107.132.127.9
107.640.940.2
107.641.140.5
107.646.448.2
107.152.256.7
106.063.271.8
104.274.083.6
102.982.991.7
101.890.095.1

Spectral data

UV-Vis
λmax? nm
Extinction coefficient, ε?
IR
Major absorption bands? cm−1
NMR
Proton NMR
Carbon-13 NMR
Other NMR data
MS
Masses of main fragments

Safety data

Formic acid
EINECS number200-579-1
Safety data
EU classificationCorrosive (C)
PEL5 ppm (9 mg/m3)
IDLH30 ppm
Autoignition temperature520 °C
Explosive limits18–51%
  • . Chemical Information Research Information Center. Archived from on 2 August 2002.