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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

Data source

Reference Type:
Vapor Pressures of Gallium Trifluoride, Trichloride, and Triiodide and Their Standard Sublimation Enthalpies
Bruno Brunetti, Vincenzo Piacente, and Paolo Scardala
Bibliographic source:
Journal of Chemical Engineering Data, 55: 98-102

Materials and methods

Test guideline
no guideline followed
Principles of method if other than guideline:
In the present investigation, further measurements of vapor pressures of these gallium trihalides were made by using a torsion assembly, and the sublimation enthalpies were derived from a second- and third-law treatment of the data. As all compounds are very hygroscopic, the cells were loaded in an efficient drybox and rapidly evacuated. The assembly used is practically the same as that described in an our previous work.15 For each of the compounds the pressure measurements in each run were made randomly in both ascending and descending temperature steps even though the data is reported in the tables as ascending. Three conventional graphite torsion cells with both effusion holes having a nominal diameter of 0.5 mm (cell A), 1.0 mm (cell B), and 1.6 mm (cell C) were used. The instrumental constants of these cells necessary to convert the measured torsion angles into pressure values were determined and checked in runs carried out before and during the study of the compounds by vaporizing very pure standards, the vapor pressures of which are well-known, in two different temperature ranges. In particular lead16 from (850 to 1100) K and benzoic acid17 from (300 to 400) K were used as standards. The torsion constants so obtained were found reproducible within about (5 to 8) % of their average values. Cell A was also employed to measure vapor pressures by the Knudsen method using the well-known equation18 p ) K·dg/ dt · (T/M)1/2. The constant K necessary to convert the rate of mass loss of the sample (dg/dt) at the experimental temperature T to pressure values was evaluated using benzoic acid in separate experiments, where M is the molecular weight of the vapor. The rate of mass loss of the sample was measured by a vacuum thermobalance (Chan 1000) to which the torsion assembly was suspended.
GLP compliance:
not specified
Type of method:
effusion method: Knudsen cell
and via the torsion effusion method

Test material

Constituent 1
Chemical structure
Reference substance name:
Gallium trichloride
EC Number:
EC Name:
Gallium trichloride
Cas Number:
Molecular formula:
gallium trichloride
Test material form:
not specified

Results and discussion

Vapour pressureopen allclose all
Key result
Test no.:
293 K
Vapour pressure:
7.48 Pa
Test no.:
298 K
Vapour pressure:
14.83 Pa

Any other information on results incl. tables

temperature depence of the vapour pressure for GaCl3 according to torsion method:

log(p/Pa) = 13.80 -3800/(T/K) (from 289 to 308 K)

Applicant's summary and conclusion

The vapour pressure of GaCl3 at 20°C (293 K) is 7.48 Pa according to Knudsen method. The temperature depence of the vapour pressure of GaCl3 according to the torsion method is log(p/Pa) = 13.80 - 3800/(T/K) (from 289 to 308 K).