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Physical & Chemical properties

Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Deviations:
no
GLP compliance:
no
Type of method:
static method
Key result
Temp.:
20 °C
Vapour pressure:
1.349 Pa
Key result
Temp.:
25 °C
Vapour pressure:
2.201 Pa

The experimental results of vapor pressure of heptanoic acid were reported in the following table:

 

t°C

T(K)

P(Pa)

1/T (K-1)

Log(P)

10,16

283,31

0,4853

0,00353

-0,3139

20,08

293,24

1,2785

0,00341

0,1067

20,10

293,26

1,3302

0,00341

0,1239

40,03

313,18

9,4922

0,00319

0,9774

40,04

313,19

9,3759

0,00319

0,9720

61,21

334,37

49,333

0,00299

1,6931

79,98

353,13

189,58

0,00283

2,2778

79,98

353,13

188,94

0,00283

2,2763

79,98

353,13

188,16

0,00283

2,2745

 

 

The equation of Clapeyron is applied to the result and a graph is obtained.

 (correlation coefficient R2= 0,9996)

According to the graph, the vapor pressure is extrapolated at several temperatures (see the table below):

 

t°C

P(Pa)

60

44,98

50

20,30

40

8,712

30

3,535

25

2,201

20

1,349

10

0,4807
Conclusions:
The vapor pressure of heptanoic acid is 1,349 Pa at 20°C or 2,201 Pa at 25°C.
Executive summary:

The vapor pressure of heptanoic acid was carried out according to the static method. Several measurements of vapor pressure and temperature have been reported in the range of 10°C to 80°C.

The vapor pressure at 20°C and 25°C was estimated thank to the curve log p versus 1/T curve:

- 1,349 Pa at 20°C

- 2,201 Pa at 25°C.

Description of key information

 The vapour pressure of Heptanoic acid is 1,349 Pa at 20°C and 2,201 Pa at 25°C.

Key value for chemical safety assessment

Vapour pressure:
1.35 Pa
at the temperature of:
20 °C

Additional information

An experimental study compliant with the guideline (OCDE 104), selected as the Key Study, showed that the vapor pressure of heptanoic acid was 1,349 Pa at 20°C and 2,201 Pa at 25°C.

Therefore heptanoic acid is considered to have low volatility.