Formic acid (data page)

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.

• MSDS from FLUKA in the SDSdata.org database
• Science Stuff

Structure and properties

Structure and properties
Index of refraction, nD	1.3714 at 20 °C
Abbe number	?
Dielectric constant, εr	58.5 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 tension	37.67 dyn/cm at 20 °C
Viscosity[2]	2.2469 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

Thermodynamic properties

Phase behavior
Triple point	281.40 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, Sosolid	? J/(mol K)
Heat capacity, cp	74.5 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, Soliquid	129.0 J/(mol K)
Enthalpy of combustion, ΔcHo	–254.6 kJ/mol
Heat capacity, cp	101.3 J/(mol K) at 20–100 °C
Gas properties
Std enthalpy change of formation, ΔfHogas	–362.6 kJ/mol
Standard molar entropy, Sogas	251.0 J/(mol K)
Heat capacity, cp	45.68 J/(mol K) at 25 °C

Vapor pressure of liquid

P in mm Hg		1	10	40	100	400	760
T in °C		–20.0(s)	2.1(s)	24.0	43.8	80.3	100.6

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

Distillation data

Vapor-liquid Equilibrium for Formic acid/Water[4] P = 760 mmHg
BP Temp. °C	% by mole water
	liquid	vapor
102.3	4.05	2.45
104.6	15.5	10.2
105.9	21.8	16.2
107.1	32.1	27.9
107.6	40.9	40.2
107.6	41.1	40.5
107.6	46.4	48.2
107.1	52.2	56.7
106.0	63.2	71.8
104.2	74.0	83.6
102.9	82.9	91.7
101.8	90.0	95.1

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 number	200-579-1
Safety data
EU classification	Corrosive (C)
PEL	5 ppm (9 mg/m3)
IDLH	30 ppm
Autoignition temperature	520 °C
Explosive limits	18–51%

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• Except where noted otherwise, data relate to Standard temperature and pressure.
• Reliability of data general note.