# Antoine Constant

on . Posted in Classical Mechanics

The Antoine constants are used in the Antoine equation to estimate the vapor pressure of a substance.

### For water, the Antoine constants depend on the temperature range

Here are two common sets of constants for water  -

• For the temperature range 1°C to 100°C (or 273.15 °K to 373.15 °K)  -
• $$A \;=\; 8.07131$$
• $$B \;=\; 1730.63$$
• $$C \;=\; 233.426$$
• For the temperature range 99°C to 374°C (or 372.15 °K to 647.15 °K)  -

• $$A \;=\; 8.14019$$
• $$B \;=\; 1810.94$$
• $$C \;=\; 244.485$$

### Units for the Constants

• A is dimensionless
• B in degrees Celsius (°C) or Kelvin (°K)
• C in degrees Celsius (°C) or Kelvin (°K)

The vapor pressure P is typically expressed in mmHg (torr) when using the Antoine equation.  A millimetre of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high, and currently defined as exactly 133.322387415 pascals or exactly 133.322 pascals.  It is denoted mmHg or mm Hg.

### Antoine constant Formula

$$log_{10} \; (P) \;=\; A - (B \;/\; C + T)$$
Symbol English Metric
$$P$$ = vapor pressure - $$mmHg$$
$$A$$ = Antoine constant $$dimensionless$$ $$dimensionless$$
$$B$$ = Antoine constant $$K$$ $$C$$
$$C$$ = Antoine constant $$K$$ $$C$$
$$T$$ = temperature $$K$$ $$C$$

Tags: Pressure Vapor