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Vapour pressure

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Endpoint:
vapour pressure
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
DTPMP (1-3Na) is a member of the DTPMP category, which is comprised of the acid form and any simple salts of the same acid.

The category hypothesis is that all the members are various ionised forms of the same parent acid. This category covers various sodium, potassium and ammonium salts of diethylene triamine penta(methylene phosphonic acid). The different salts are prepared by neutralising the acid to a specific pH and accordingly the proportions of the constituents and their degree of ionisation are comparable between substances under similar conditions (in vivo and in the environment). All category members are based on the DTPMP structure. Data are available for the acid form and some salts.

The read-across is therefore based on the presence of common functional groups in both the acid and the salt. The main assumption is that sodium is not significant in respect of all the properties under consideration. The sodium salt is expected to decompose before boiling and have a high melting temperature.
Reason / purpose for cross-reference:
read-across source
Key result
Test no.:
#1
Temp.:
25 °C
Vapour pressure:
0 Pa
Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
Please refer to attached justification documents
Principles of method if other than guideline:
Estimation by MPBPVP program, USEPA/Syracuse Research, v1.40
Key result
Test no.:
#1
Temp.:
25 °C
Vapour pressure:
0 Pa
Conclusions:
A vapour pressure value of 2.7E-09 Pa at 25°C was obtained for DTPMP-H using a relevant estimation method. The result is considered to be reliable.

Description of key information

Vapour pressure [DTPMP (1-3Na)]: < 2.7E-09 Pa at 25°C (QSAR)

Key value for chemical safety assessment

Vapour pressure:
0 Pa
at the temperature of:
25 °C

Additional information

The vapour pressure of the sodium salt of DTPMP has been read-across from the parent acid (DTPMP-H). A predicted vapour pressure of 2.7E-9 Pa at 25°C was obtained for DTPMP-H using an accepted calculation method (MPBPVP program, USEPA/Syracuse Research, v1.43). This predicted value is read-across to the salt, DTPMP (1-3Na) as <2.7E-9 Pa at 25°C since the vapour pressure of the salt is expected to be lower than that of the parent acid. The result (Fisk 2010) is considered to be reliable and is selected as a key study.

 

The minor constituents are phosphonate salts that are structurally similar to the main constituent or inorganic salts; all will have negligible vapour pressure.