# 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, n$_D$ | 1.3714 at 20 °C |
| Abbe number | ? |
| Dielectric constant, ε$_r$ | 58.5 ε$_0$ at 16 °C measured at 400 MHz |
| Bond strength | ? |
| Bond length | C=O bond: 123 pm C–OH bond: 136 pm |
| Bond angle | ? |
| Magnetic susceptibility | ? |
| Surface tension | 37.67 dyn/cm at 20 °C |
| Viscosity | 2.2469 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 point | 281.40 K (8.25 °C), 2.2 kPa |
| Critical point | 588 K (315 °C), 5.81 MPa |
| Std enthalpy change of fusion, Δ$_{fus}$H$^o$ | +12.68 kJ/mol |
| Std entropy change of fusion, Δ$_{fus}$S$^o$ | +45.05 J/(mol·K) at 8.25 °C |
| Std enthalpy change of vaporization, Δ$_{vap}$H$^o$ | +23.1 kJ/mol |
| Std entropy change of vaporization, Δ$_{vap}$S$^o$ | +61.8 J/(mol·K) |
| Solid properties ||
| Std enthalpy change of formation, Δ$_f$H$^o$$_{solid}$ | ? kJ/mol |
| Standard molar entropy, S$^o$$_{solid}$ | ? J/(mol K) |
| Heat capacity, c$_p$ | 74.5 J/(mol K) at –22 °C 82.8 J/(mol K) at 0 °C |
| Liquid properties ||
| Std enthalpy change of formation, Δ$_f$H$^o$$_{liquid}$ | –425.5 kJ/mol |
| Standard molar entropy, S$^o$$_{liquid}$ | 129.0 J/(mol K) |
| Enthalpy of combustion, Δ$_c$H$^o$ | –254.6 kJ/mol |
| Heat capacity, c$_p$ | 101.3 J/(mol K) at 20–100 °C |
| Gas properties ||
| Std enthalpy change of formation, Δ$_f$H$^o$$_{gas}$ | –362.6 kJ/mol |
| Standard molar entropy, S$^o$$_{gas}$ | 251.0 J/(mol K) |
| Heat capacity, c$_p$ | 45.68 J/(mol K) at 25 °C |

## Vapor pressure of liquid

| P in mm Hg | P in mm Hg | 1 | 10 | 40 | 100 | 400 | 760 |
| T in °C | 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.

## Distillation data

Vapor-liquid Equilibrium for Formic acid/Water P = 760 mmHg :
| BP Temp. °C | % by mole water | % by mole water |
| BP Temp. °C | 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 :
| λ$_{max}$ | ? 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/m$^3$) |
| IDLH | 30 ppm |
| Autoignition temperature | 520 °C |
| Explosive limits | 18–51% |
* view
* Except where noted otherwise, data relate to Standard temperature and pressure.
* Reliability of data general note.