Formic acid (data page)

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This page provides supplementary chemical data on formic acid.

Material Safety Data Sheet[edit]

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.

Structure and properties[edit]

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 length[1]C=O bond: 123 pm
C–OH bond: 136 pm
Bond angle ?
Magnetic susceptibility ?
Surface tension37.67 dyn/cm at 20°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[edit]

Phase behavior
Triple point281.40 K (8.25 °C), 2.2 kPa
Critical point[3]588 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,
 ? 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,
129.0 J/(mol K)
Enthalpy of combustion, ΔcHo–254.6 kJ/mol
Heat capacity, cp101.3 J/(mol K) at 20°C-100°C
Gas properties
Std enthalpy change
of formation
, ΔfHogas
–362.6 kJ/mol
Standard molar entropy,
251.0 J/(mol K)
Heat capacity, cp45.68 J/(mol K) at 25°C

Vapor pressure of liquid[edit]

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: \scriptstyle \log_{10} P_{mmHg} = 6.94459 - \frac {1295.26} {218.0+T} obtained from Lange's Handbook of Chemistry, 10th ed.

Distillation data[edit]

Vapor-liquid Equilibrium for Formic acid/Water[4]
P = 760 mmHg
 % by mole water

Spectral data[edit]

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

Safety data[edit]

Formic acid
EINECS number200-579-1
Safety data
EU classificationCorrosive (C)
PEL5 ppm (9 mg/m3)
IDLH30 ppm
Autoignition temperature520°C
Explosive limits18–51%


  1. ^ Morrison, Robert Thornton and Boyd, Robert Neilson, Organic Chemistry, 2nd ed. Allyn and Bacon 1972, p 596
  2. ^ Lange's Handbook of Chemistry, 10th ed. pp 1669-1674
  3. ^ Thornton Schnabel, Marfa Cortada, Jadran Vrabec, Santiago Lago, Hans Hasse. "Molecular Model for Formic Acid adusted to Vapor-Liquid Equilibrium". Insitut für Technische Thermodynamik und Thermische Verfahrenstechnik (Institute for Technical Thermodynamic and Thermal Process Engineering), Universität Stuttgart. Retrieved 3 May 2007. 
  4. ^ "Binary Vapor-Liquid Equilibrium Data" (Queriable database). Chemical Engineering Research Information Center. Retrieved 6 May 2007. 

Except where noted otherwise, data relate to standard ambient temperature and pressure.

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