Silicon tetrachloride

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

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:

The test apparatus consisted of a Carius tube (a 35 ml Pyrex@ glass tube with an adapter at the outlet with a glass to metal seal) fitted with a Swagelock three way valve. One end of the valve was connected via a stainless steel tube with a 1/16” capillary bore to a calibrated 0 to 30 PSI pressure transducer. The other end was connected to a vacuum pump through a cold trap filled with liquid nitrogen. The entire assembly was leak checked before the experiments. The system was calibrated with acetone and methanol. The Carius tube, under nitrogen flow, was filled with the silane sample and then connected to a pressure transducer and the vacuum pump as described above. The system was evacuated several times until a constant pressure reading was observed in the pressure transducer. The connection to the vacuum pump was disconnected and the Carius tube containing the sample was placed in a bath at 20°C.The constant pressure reading after an equilibration time (20 minutes) was noted as the vapour pressure of the sample at 20°C. The entire process was repeated until two pressure values that were very nearly the same.

GLP compliance:

no

Type of method:

other: Carius tube

Key result

Test no.:

#1

Temp.:

20 °C

Vapour pressure:

291.9 hPa

Test 1: 213.01 mm Hg (4.12 PSI) 
Test 2: 224.9 mm Hg (4.35 PSI) 
Mean: 218.96 mm Hg (4.24 PSI)

Conclusions:

A vapour pressure value of 291.9 hPa at 20°C was determined for the substance in a reliable study conducted according to generally accepted scientific principles.

Description of key information

Vapour pressure [silicon tetrachloride]: 29200 Pa at 20°C

Vapour pressure [silicic acid]: negligible

Key value for chemical safety assessment

Vapour pressure:

29 200 Pa

at the temperature of:

20 °C

Additional information

A vapour pressure value of 29200 Pa at 20°C was determined for the submission substance using a relevant test method but not in compliance with a known quality system. The result is considered to be reliable and is selected as key study.

The key study is supported by vapour pressure value of approximately 32000 Pa (239 mmHg) at 25.1°C using an isoteniscope method (Jenkins 1954). In Bimsner 2000, vapour pressure values of 22000 Pa at 10°C, 34000 Pa at 20°C and 50000 Pa at 30°C were obtained for the substance using relevant test method. In other reliable data, vapour pressure values of approximately 31400 Pa at 20°C and 29000 Pa at 20°C were obtained for the submission substance.

In available secondary sources to which reliability could not be assigned, vapour pressure values of approximately 26000 Pa at 20°C, 25700 Pa at 20°C, 32000 Pa at 25-25.5°C, 41300 Pa at 108.39°C and 1728000 Pa at 185.25°C were reported for the substance.

All the available vapour pressure data are in agreement that the submission substance is a highly volatile substance.

In contact with water, silicon tetrachloride reacts very rapidly to form silicic acid hydrochloric acid.

Silicic acid is expected to have negligible vapour pressure.