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Vapour pressure

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vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Principles of method if other than guideline:
Critical Point and Vapour Pressure Measurements by means of a Flow Method with Ultra-low Residence Times.
GLP compliance:
Type of method:
other: Critical Point and Vapour Pressure Measurements by means of a Flow Method with Ultra-low Residence Times.
Key result
Test no.:
22.5 °C
Vapour pressure:
72 188 Pa
Transition / decomposition:

Table 1. Results of the critical point measurements for trichlorosilane

Tc, K                      P, psia
meas         prev.    est.(1)      meas.        est.(a)
474.2±1.5  479(b)   479          569.9±2%    587

(a) Estimated by the first order method of Wilson and Jasperson (Poling et al., 2001) using the boiling point obtained as part of this project  
(b)Matthews, J.F. The Critical Constants of Inorganic Substances, Chem Rev, 72,71 (1972); Only a critical temperature is reported.

Table 2. Vapour Pressure of trichlorosilane.
                      P, psia
T, K       measured          correlated(a)       % dev
474.2      569.9             565.7              -0.73%      
                                           (measured Tc, Pc)
473.5      563.3             560.5               -0.49%     
                                           (This work)
472.8      551.5             554.9               0.62%
469.8      526.7             531.5               0.91%
459.4      457.3             456.4              -0.20%
450.3      398.2             397.8              -0.10%
304.8      14.52             14.53               0.12%      
(Jenkins and Chambers 1954)
300.2      12.35             12.35               -0.07%     
295.7      10.50             10.47               -0 31%
291.9      9.028             9.062               0.38%
283.3      6.447             6.437               -0.16%
275.3      4.579             4.581               0.05%
a. Riedel parameters- A= 36.3995, B= -4263.80, C= -3.45244,
D= 0.179014x10-16
Normal boiling point 305.1 K

The results of the critical point measurements are given in Table 1. This table lists the measured and estimated critical temperature (Tc) and pressure (Pc) The estimated uncertainties are also listed with each measured value. The estimated Tc and Pc, are based on atomic contributions (see the first order method of Wilson and Jasperson, (as given in Poling, B. E., Prausnitz, J M., O’ Connell, J. P., The Properties of Gases and Liquids 5th edition; McGraw-Hill. New York, 2001) using the boiling point obtained as part of this project. The critical temperature reported by Matthews, J. F. (The Critical Constants of Inorganic Substances, Chem Rev, 72, 71. 1972) is also given. Table 2 reports the measured vapor pressure data for trichlorosilane. This table lists the measured temperatures and the measured and correlated vapor pressures. Measured literature values (Jenkins, A. C., Chambers, G. F., Vapor Pressures of Silicon Compounds, Ind Eng Chem, 46, 2367 (1954) are also included in this table. The data are fitted to the Riedel equation using four parameters, and the resulting parameters are given at the bottom of Table 2. 

The Riedel equation has the following form: ln(P, psia) = A + B/T,K + C ln(T, K) + D(T, K) 

where A, B, C, and D are parameters used to obtain the best fit of the measured data. 

Both the data measured at Wiltec and the literature data were used to obtain the reported correlation The vapor pressures measured at Wiltec are estimated to be accurate to within ±0.5 K in the temperature and ±2% in the pressure.

A vapour pressure value of 72188 Pa at 22.5°C was determined for the substance in a reliable study conducted according to generally accepted scientific principles.

Description of key information

Vapour pressure [trichlorosilane]: 72000 Pa at 22.5°C

Vapour pressure [silanetriol]: negligible

Vapour pressure [silicic acid]: negligible

Key value for chemical safety assessment

Vapour pressure:
72 000 Pa
at the temperature of:
22.5 °C

Additional information

Several reliable vapour pressure values are available for trichlorosilane. A measured vapour pressure value of approximately 72200 Pa at 20°C was determined for the submission substance using a relevant test method. The result is considered to be reliable and is selected as key study.

Further vapour pressure values of 69400 Pa at 20°C, 70660 Pa at 20°C, 79047 Pa at 20°C, 65600 Pa at 20°C 65000 Pa at 20°C, 62200 Pa at 18.7°C and >4.2E+7 Pa at 206°C were determined or reported for the substance using relevant test methods.

In available secondary sources to which reliability could not be assigned, vapour pressure values of 65600 Pa at 20°C and 66500 Pa at 20°C were reported for the substance.

Variations in the vapour pressure may be caused by differences in test method or test substance purity. All values are consistent with the substance being highly volatile. The key study is selected as the most recent study for which details of the test methods are available.

In contact with water, the substance hydrolyses very rapidly to form silanetriol as the intermediate hydrolysis product; the ultimate hydrolysis product is monosilicic acid, hydrochloric acid and hydrogen.

Both silicon-containing hydrolysis products are expected to have negligible vapour pressure.