Nickel, 5-[2-(2-hydroxy-3,7-disulfo-1-naphthalenyl)diazenyl]-1H-1,2,4-triazole-3-carboxylate sodium complexes

Vapour pressure

Administrative data

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Study initiation 30th October 2002, Experimental phase 13th November 2002-17th January 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Meets the criteria for classification as Reliable without restriction according to Klimisch et al (1997)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

GLP compliance:

yes

Type of method:

effusion method: by loss of weight or by trapping vaporisate

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

443-510-2

EC Name:

-

Cas Number:

738587-10-5

Molecular formula:

C26H14N10Ni2O18S4 as free acid

IUPAC Name:

dinickel(2+) sodium 3-carboxy-5-[(1E)-2-(7-oxido-2,6-disulfonaphthalen-1-yl)diazen-1-yl]-1H-1,2,4-triazol-1-ide 3-carboxy-5-[(1E)-2-(7-oxido-2-sulfo-6-sulfonatonaphthalen-1-yl)diazen-1-yl]-1H-1,2,4-triazol-1-ide

Results and discussion

Vapour pressure

Temp.:

25 °C

Vapour pressure:

< 0.001 Pa

Remarks on result:

other: First vapour pressure

Any other information on results incl. tables

The vapour pressure was expected to be too low to measure in the preferred temperature range of 0- 50°C, and a higher temperature range was therefore necessary. DSC scans carried out on the substance to determine boiling point (Figure 1 see attached background material) showed endothermic behaviour initiating around 120°C. Two measurements were therefore made at 83.8 and 110.1 °C. While the displacement due to weight loss is small, the accuracy of the determinations is less good than is often observed, and the data at 110.1 °C is particularly poor: regression analysis effectively shows no evidence of displacement at the 5% significance level, i.e. the 95% confidence interval for the slope includes zero. A further measurement was therefore made at 71.3°C. Although this temperature is really too close to the first measurement to give data suitable for accurate extrapolation via a Log P versus 1/T plot, it was felt to be more important to measure at a temperature well below the observed endotherm, and a lower temperature might have generated a displacement below the sensitivity limit of the instrument. The measured data is reported overleaf and the displacement plots are attached as Figures 2 - 4.(see attached background material) Note that in all of the runs, some early data has been excluded from the regression. This initial relatively rapid loss, which precedes the steady state displacement associated with the substance vapour pressure, is associated with the loss of traces of solvent or volatiles, in this case probably water.

Temperature Vapour Pressure

t/°C                      PIP a

71.3                      3.23 x 10-3

83.8                     2.96 x 10-3

110.1                   1.46 X 10-3

The measured vapour pressure at 110.1°C has not been used further as discussed above. The data at 71.3 and 83.8°C are apparently inconsistent, as vapour pressure increases with temperature. The difference is small, however, and not statistically significant (the 95% confidence intervals for the two displacement rates are virtually identical and both include both best fit slopes).

The data are therefore best regarded as near duplicate measurements, giving a mean vapour pressure of 3.10 x 10-3pa (2.32 x 10-5 torr) at a mean temperature of 77.6°C. In the absence of a Log P versus 1fT plot, the approximate vapour pressure at 25°C can be calculated from this result based on the established relationship that vapour pressure approximately doubles for each 10K rise in temperature. Thus:-P2 = P1 x 2 (T2-T1)/10

On this basis, the vapour pressure at 25°C is estimated to be ca. 8 x 10-5 Pa (6 x 10-7 torr). In practice, the rate of change of vapour pressure with temperature varies and can be as low as a 40% increase in vapour pressure for each 10K rise in temperature. This would give a conservative (high) estimate of the vapour pressure at 25°C of ca. 5 x 10-4 Pa (4 x 10-6torr).

In case the relatively poor accuracy in measuring vapour pressure arose due to thermal instability of the substance, two thermogravimetric runs (Figures 5 & 6, see attached background material) were performed to check for weight loss in the region of the endotherm of Figure 1 (see attached background material) The first run (03005011) (see attached background material), a ramped scan from 25 - 250°C at 10°C/min, gave a smooth pattern of weight loss over the run amounting to 18.7% of the initial mass. This does not suggest that the weight loss is associated with the observed endotherm. As the weight had not stabilised by the end of the run, a further isothermal run (03005021) (see attcahed background material) at 100°C was performed. This again gave a smooth weight loss pattern followed by a stable weight: total weight loss being 19.8% of the original mass. As the analytical data provided by the Sponsor indicates the presence of water in the sample, this is the most likely explanation of the weight loss observed. No evidence of thermal instability of the base material in the region of the vapour pressure measurements was found.

Applicant's summary and conclusion

Conclusions:

The vapour pressure of the test substance is < 5 x 10-4Pa (4 x 10-6 torr) at 25°C.

Executive summary:

Introduction:

The method used was the Knudsen effusion procedure, which is an approved method for Test A4 of Reference 6.1.

Results and conclusion:

The vapour pressure of the test substance is < 5 x 10-4Pa (4 x 10-6 torr) at 25°C.