Naphthenic acids

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Remarks:

ASTM guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

GLP compliance:

yes

Type of method:

flask method

Specific details on test material used for the study:

Specific analyses of the test substance:

Acid number: 235 mg KOH/gm
Unsaponifiables (total): 4.9%
Viscosity @40°C: 32 cst
Specific gravity @20°C: 0.969
Color (Garner), GI 4.5
Water content: 0.07%
Phenolic content (acid): 0.31%
Total sulfur: 0.34
CP – Flash point °F (COC): 343

Water solubility:

ca. 88.1 mg/L

Temp.:

20 °C

pH:

>= 7.5

Details on results:

The solubility value represented the measured concentration of total dissolved naphthenic acids in the water accommodated fraction of freshwater algal nutrient medium (pH 7.5) using a loading rate of 100 mg/L. Higher solubility concentrations may be achieved using higher loading rates.

Conclusions:

The solubility of naphtenic acids is low and has a value of about 88.1 mg/L.
Interpretation of results: slightly soluble (0.1-100 mg/L)

Reference 2

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2010

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Principles of method if other than guideline:

Data were taken from a peer-reviewed article or handbook.

Water solubility:

< 50 mg/L

Temp.:

20 °C

Although no temperature reported it was assumed that the results reflect ambient temperature.

Conclusions:

The water solubility of naphthenic acids was reported to be <50 mg/L at 20°C under the presented conditions.
Interpretation of results: slightly soluble (0.1-100 mg/L)

Description of key information

The water solubility of naphthenic acids determined by an experimental study (HPVIS, 2009) considered reliable without restrictions (K1) and assigned as key study is about 88.1 mg/L. This value has been experimentally determined using the flask method. In literature (Kirk-Othmer, 1995) a value of <50 mg/L at 20°C was reported and was assigned as supporting study considered reliable with restrictions (K2). 

Key value for chemical safety assessment

Water solubility:

88.1 mg/L

at the temperature of:

20 °C

Additional information

Although water solubility will vary depending on the compositional make-up of the naphthenic acids, the sample used in the experimental test is representative for the registered substance. The result of 88.1 mg/l is therefore considered to be representative for the registered substance.