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Henry's Law constant

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Endpoint:
Henry's law constant
Type of information:
other: EU Risk Assessment
Adequacy of study:
other information
Reliability:
other: EU Risk Assessment
Rationale for reliability incl. deficiencies:
other: No reliability is given as this is a summary entry for the EU RAR.
Principles of method if other than guideline:
EU Risk Assessment
GLP compliance:
not specified

EU Risk Assessment (2003):


 


Conclusion on volatility


The volatilisation of 1,2,4-TCB in clean water may be high but will be reduced in natural surface water according to the depth of the water body, possible stratification or turbulence of the water body and to the content of dissolved organic carbon (DOC) and particulate organic carbon (POC). The volatilisation is slow from soil and sludge because adsorption to organic carbon takes place.


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Volatility


Volatilisation from surface water is estimated by means of 1,2,4-TCB¿s Henry¿s Law constant (H). Using a vapour pressure of 36 Pa at 20°C and a water solubility of 36 mg/l, the estimated Henry's Law constant would be 181 Pa*m3/mol which indicates that volatilisation from shallow waters and after accidental spillage to water may take place.


 


A more reliable value may be obtained by measuring H directly by direct measurement of concentrations in the gas phase and the water phase in a system at equilibrium. Using a gas-purge technique, a water concentration of 10µg/l and GC determination, ten Hulscher et al. (1992) measured the dimensionless Henry¿s Law constant (Kair-water) to 0.041 equivalent to a H of 101 Pa.m3/mol for 1,2,4-TCB. The measurements were carried out in a buffer solution at pH 6.4 which may have changed the solubility of 1,2,4 -TCB. Other measured values ofH at 20ºC were 122 Pa.m3/mol(Kair-water 0.050) and 185 Pa.m3/mol (Kair-water 0.076) (Oliver, 1985; Ashworth et al., 1988, respectively).


 


QSAR estimation of Henry's Law constant by the bond contribution method resulted in a H estimated to be 2.19*10-3 atm.m3/mol (290 Pa.m3/mol) (EPIWIN, 1995).


 


The volatilisation rate in an aqueous solution has been observed to be 6.5 hour/m depth at 20°C (Geyer et al., 1985). The volatility from an aqueous solution was studied using the water sampling method. The initial concentration was 10.7 mg/l and the half-life was estimated to be 22 minutes at 20°C using 14C-labelled substance (Korte and Freitag, 1986). These studies confirm that volatilisation takes place but the results are not in a form that can be used quantitatively in this risk assessment.


 


The volatilisation from soil is reduced at increasing content of organic matter due to adsorption. In soil incubated with 1,2,4-TCB at the concentration 50 ppm, the amount of volatile substances recovered from the test systems was 4 to 18% of the initial concentration from soil with high organic matter and 20 to 40% at low organic matter (Marinucci and Bartha, 1979).

Executive summary:

EU Risk Assessment, 2003:



The volatilisation of 1,2,4-TCB in clean water may be high but will be reduced in natural surface water according to the depth of the water body, possible stratification or turbulence of the water body and to the content of dissolved organic carbon (DOC) and particulate organic carbon (POC). The volatilisation is slow from soil and sludge because adsorption to organic carbon takes place.
Volatilisation from surface water is estimated by means of 1,2,4-TCB Henry's Law constant (H). Using a vapour pressure of 36 Pa at 20°C and a water solubility of 36 mg/L, the estimated Henry's Law constant would be 181 Pa*m3/mol which indicates that volatilisation from shallow waters and after accidental spillage to water may take place
A more reliable value may be obtained by measuring H directly by direct measurement of concentrations in the gas phase and the water phase in a system at equilibrium. Using a gas-purge technique, a water concentration of 10µg/l and GC determination, ten Hulscher et al. (1992) measured the dimensionless Henry's Law constant (Kair-water) to 0.041 equivalent to a H of 101 Pa.m3/mol for 1,2,4-TCB. The measurements were carried out in a buffer solution at pH 6.4 which may have changed the solubility of 1,2,4 -TCB. Other measured values ofH at 20ºC were 122 Pa.m3/mol(Kair-water 0.050) and 185 Pa.m3/mol (Kair-water 0.076) (Oliver, 1985; Ashworth et al., 1988, respectively).
QSAR estimation of Henry's Law constant by the bond contribution method resulted in a H estimated to be 2.19*10-3 atm.m3/mol (290 Pa.m3/mol) (EPIWIN, 1995).
The volatilisation rate in an aqueous solution has been observed to be 6.5 hour/m depth at 20°C (Geyer et al., 1985). The volatility from an aqueous solution was studied using the water sampling method. The initial concentration was 10.7 mg/l and the half-life was estimated to be 22 minutes at 20°C using 14C-labelled substance (Korte and Freitag, 1986). These studies confirm that volatilisation takes place but the results are not in a form that can be used quantitatively in this risk assessment.
The volatilisation from soil is reduced at increasing content of organic matter due to adsorption. In soil incubated with 1,2,4-TCB at the concentration 50 ppm, the amount of volatile substances recovered from the test systems was 4 to 18% of the initial concentration from soil with high organic matter and 20 to 40% at low organic matter (Marinucci and Bartha, 1979).

Endpoint:
Henry's law constant
Type of information:
experimental study
Adequacy of study:
other information
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Original reference is not available.
GLP compliance:
not specified
Executive summary:

Bayer SDS, 1986:



Henry constant is 108.4 Pa m3/mol.

Endpoint:
Henry's law constant
Type of information:
experimental study
Adequacy of study:
other information
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Original reference is not available.
GLP compliance:
not specified
Executive summary:

WHO, 1991:


Henry constant is 0.439 kPa m3/mol. 

Endpoint:
Henry's law constant
Type of information:
experimental study
Adequacy of study:
other information
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Original reference is not available.
GLP compliance:
not specified
Executive summary:

Rippen, 1991:



Henry-Coefficient: 0.077 at 20°C (calculated); 0.093 at 25°C (calculated)

Endpoint:
Henry's law constant
Type of information:
experimental study
Adequacy of study:
other information
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Original reference is not available.
GLP compliance:
not specified
Executive summary:

Mackay, 1992:


Henry constant is 277 Pa m3/mol (calculated).

Endpoint:
Henry's law constant
Type of information:
experimental study
Adequacy of study:
other information
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Original reference is not available.
GLP compliance:
not specified
Executive summary:

Howard, 1989:



Henry's law constant is 1.42 x 10e-3 atm-m3/mol (calculated from water solubility and vapour pressure).

Endpoint:
Henry's law constant
Type of information:
experimental study
Adequacy of study:
other information
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Original reference is not available.
GLP compliance:
not specified
Executive summary:

Umweltbundesamt (UBA), 1984:



volatility from aqueous solutions:
calculated: t 1/2 (1 m depth, 25 °C)= 25 x 10 E 3 s (7.0 hours)
measured: t1/2 (1 m depth, 20 °C)=23 x 10 E 3 s (6.5 hours)
evaporation from water (10 cm depth): t1/2 = approx. 45 min. (calculated)

Description of key information

For transported isolated intermediates according to REACh, Article 18, this endpoint is not a data requirement. However, data is available for this endpoint and is thus reported under the guidance of "all available data".


 


Howard, 1989:
Henry's law constant is 1.42 x 10e-3 atm-m3/mol (calculated from water solubility and vapour pressure).



Mackay, 1992:
Henry constant is 277 Pa m3/mol (calculated).



Rippen, 1991:
Henry-Coefficient: 0.077 at 20°C (calculated); 0.093 at 25°C (calculated)
Umweltbundesamt (UBA), 1984:
volatility from aqueous solutions:
calculated: t 1/2 (1 m depth, 25 °C)= 25 x 10 E 3 s (7.0 hours)
measured: t1/2 (1 m depth, 20 °C)=23 x 10 E 3 s (6.5 hours)
evaporation from water (10 cm depth):
t1/2 = approx. 45 min. (calculated)



WHO, 1991:
Henry constant is 0.439 kPa m3/mol.



Bayer SDS, 1986:
Henry constant is 108.4 Pa m3/mol.



EU Risk Assessment, 2003:
The volatilisation of 1,2,4-TCB in clean water may be high but will be reduced in natural surface water according to the depth of the water body, possible stratification or turbulence of the water body and to the content of dissolved organic carbon (DOC) and particulate organic carbon (POC). The volatilisation is slow from soil and sludge because adsorption to organic carbon takes place.
Volatilisation from surface water is estimated by means of 1,2,4-TCBs Henry's Law constant (H). Using a vapour pressure of 36 Pa at 20°C and a water solubility of 36 mg/l, the estimated Henry's Law constant would be 181 Pa*m3/mol which indicates that volatilisation from shallow waters and after accidental spillage to water may take place
A more reliable value may be obtained by measuring H directly by direct measurement of concentrations in the gas phase and the water phase in a system at equilibrium. Using a gas-purge technique, a water concentration of 10µg/l and GC determination, ten Hulscher et al. (1992) measured the dimensionless Henry¿s Law constant (Kair-water) to 0.041 equivalent to a H of 101 Pa.m3/mol for 1,2,4-TCB. The measurements were carried out in a buffer solution at pH 6.4 which may have changed the solubility of 1,2,4 -TCB. Other measured values ofH at 20ºC were 122 Pa.m3/mol(Kair-water 0.050) and 185 Pa.m3/mol (Kair-water 0.076) (Oliver, 1985; Ashworth et al., 1988, respectively).
QSAR estimation of Henry's Law constant by the bond contribution method resulted in a H estimated to be 2.19*10-3 atm.m3/mol (290 Pa.m3/mol) (EPIWIN, 1995).
The volatilisation rate in an aqueous solution has been observed to be 6.5 hour/m depth at 20°C (Geyer et al., 1985). The volatility from an aqueous solution was studied using the water sampling method. The initial concentration was 10.7 mg/l and the half-life was estimated to be 22 minutes at 20°C using 14C-labelled substance (Korte and Freitag, 1986). These studies confirm that volatilisation takes place but the results are not in a form that can be used quantitatively in this risk assessment.
The volatilisation from soil is reduced at increasing content of organic matter due to adsorption. In soil incubated with 1,2,4-TCB at the concentration 50 ppm, the amount of volatile substances recovered from the test systems was 4 to 18% of the initial concentration from soil with high organic matter and 20 to 40% at low organic matter (Marinucci and Bartha, 1979)

Key value for chemical safety assessment

Additional information