N-[3-(dimethylamino)propyl]stearamide monoacetate

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2015-02-05 to 2015-07-13

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

EC Method A.4; OECD Method 104

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

Version / remarks:

EC Method A.4; OECD Method 104

GLP compliance:

yes (incl. QA statement)

Type of method:

effusion method: vapour pressure balance

Key result

Test no.:

#1

Temp.:

25 °C

Vapour pressure:

0.001 Pa

Calculations

Assuming no condensation, the vapour pressure is related to the observed mass difference by the relationship

Equation 1: Vapour pressure = (Δm * g) / A 

When condensation occurs the mass difference can, by reduced momentum transfer, be decreased by up to a factor of two from that appropriate to equation 1. The vapour pressure can also be obtained from the kinetic theory relationship for effusion or complete condensation

Equation 2: Vapour pressure = (C / A) * sqrt (2πRT / M)

The efficiency of the condensation may be determined from the relative magnitudes of the measured mass difference and the condensation rate. For a degree of condensation, α, the measured condensation rate must be divided by this factor (α) to obtain the maximum condensation rate to be used in equation 2. Likewise, the experimental mass differences must be modified by a factor of 2/(2-α), which gives the appropriate factor of two enhancement in the vapour pressure calculation when the molecules do not bounce back.

By equating equations 1 and 2 at a given vapour pressure, it is possible to allow for the evaluation of α at each data point:

Equation 3:   = [(2 - α) / 2α] * sqrt (2πRT / M) * (1 / g)

Rearranging equation 3 gives equation 4 from which α can be calculated directly

Equation 4: α = { [ (Δm * g) / A ] * sqrt (M / 2πRT) + 0.5 }^-1

The effect of α on the two methods for estimating vapour pressure yields identical results. Confidence in this system is demonstrated by the observation that the values of α approach, but never exceed, unity (when α=1 there is 100% condensation).

The vapour pressure-temperature relationship is as follows:

Equation 5: Log₁₀Vp = (Slope / T) + Intercept

Consequently, a plot of log₁₀Vp versus 1/T(K) should be linear, and by interpolation the vapour pressure at 298.15K can be calculated.

 

Key results	Run 1	Run 2
Correlation (r)	-0.9736	-0.9784
Slope	-3996	-3249
Intercept	10.31	7.749
Vp (Pa) at 25°C	8.0 x 10^-4	7.1 x 10^-4

The runs yielded a mean vapour pressure value at 25°C of 7.6 x 10^-4 Pa.

Conclusions:

The test substance was found to have a vapour pressure of 0.00076 Pa at 25°C.

Executive summary:

A study was performed to determine the vapour pressure of the test substance. The study was designed in accordance with accepted principles in order to meet the requirements of REACH Regulation (EU) No 1907/2006 of the European Parliament and of the Council.

The method followed is amongst those described in Commission Regulation (EC) No. 440/2008 (Method A.4) and the OECD Guidelines for the Testing of Chemicals (Method 104).

The test substance was found to have a vapour pressure of 7.6 x 10^-4 Pa at 25°C.

Description of key information

The test substance was found to have a vapour pressure of 7.6 x 10^-4 Pa at 25°C.

Key value for chemical safety assessment

Vapour pressure:

0.001 Pa

at the temperature of:

25 °C