Dierbium trioxide

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Valid with restrictions. This is peer reviewed data where the test methodology and identity of the substance have been evaluated, and a reliable and representative value for the endpoint has been selected. No information on GLP status or test guideline followed is available.

Qualifier:

no guideline available

Principles of method if other than guideline:

Handbook data does not specify the method. Data from peer reviewed source.

GLP compliance:

not specified

Type of method:

other: Not specified

Water solubility:

0 other: g-mol/L

Temp.:

29 °C

Remarks on result:

other: No pH reported.

Water solubility:

4.9 mg/L

Temp.:

29 °C

Remarks on result:

other: No pH reported. The mass-based water solubility is calculated by multiplying the molarity value (0.0000128 g-mol/L) by the molar mass in grams (382.5169 g/mol) to give 0.00490 g/L.

Conclusions:

Interpretation of results: slightly soluble (0.1-100 mg/L)
The test material has a water solubility of 0.0000128 g-mol/L (equating to 4.9 mg/L) at 29 °C and as such can be described as slightly soluble.

Executive summary:

The test material has a water solubility of 0.0000128 g-mol/L (equating to 4.9 mg/L) at 29 °C and as such can be described as slightly soluble.

Reference 2

Endpoint:

water solubility

Type of information:

not specified

Adequacy of study:

supporting study

Study period:

Not reported.

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Product information from a company Material Safety Data Sheet and accompanying product specification.

Principles of method if other than guideline:

No information provided on material and methods. Information presented as a short abstract.

GLP compliance:

not specified

Remarks on result:

other: insoluble

The test material was reported to be insoluble.

Conclusions:

Interpretation of results: other: insoluble
The test material was reported to be insoluble in water.

Executive summary:

Information on physico-chemical properties of the test material were presented as a short abstract as part of a company Material Safety Data Sheet. The test material was reported to be insoluble in water.

Reference 3

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28 September 2019 to 07 October 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

Deviations:

no

GLP compliance:

no

Type of method:

other: Transformation/Dissolution of Metals and Metal Compounds in Aqueous Media

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

ca. 1 486 µg/L

Element analysed:

Erbium

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 6
CVoverall = 5 %; N = 9

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

255 µg/L

Element analysed:

Erbium

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 8
CVoverall = 2 %; N = 9

Details on results:

- The temperature of the test solutions fluctuated between 21.4 and 21.8 °C, which was in line with the test conditions of 20 – 23 °C.
- The test material has no immediate influence on the pH of the test system. The pH measured in the medium at the start of the test, and in the blank and test material vessels during the test at pH 6 and pH 8 varied from 5.99 to 6.08 and from 8.01 to 8.03, respectively. The measured data at pH 6 and pH 8 were within the specifications of ± 0.2 units of pH.
- The dissolved oxygen concentration measured in the blank and test material vessels at pH 6 and pH 8 varied from 8.42 to 8.53 mg/L O2 and from 8.40 to 8.49 mg/L O2, respectively. These values were higher than the required value of ± 6 mg/L O2 at 22 °C, corresponding to a minimal saturation level in the air of 70 %.
- The test media at the start of the test and the blank control vessels during the test showed concentrations below or close to the limit of detection of 2 μg/L Er. The limit of detection was determined as the rounded-up values of three times the standard deviation of the element of all blank (pH 6 and pH 8) measurements in this study (N = 12).

The following observations could be made in the test vessels at the nominal pH 6 with a loading of 100 mg/L Dierbium trioxide:
- An average dissolved concentration of 1486 ± 76 μg/L Er was found at the 24 hours endpoint with a between-vessel coefficient of variation of 5 % (N = 3) which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
- Based on the specific surface area of the Dierbium trioxide powder (i.e. 0.6 m²/g test material), an erbium release per surface of 25 mg/m² was calculated at the 24 hours endpoint.
- Based on the erbium content of the test material (87.28 % Er) and the average dissolved erbium concentration, an erbium release of approximately 1.7 % could be calculated at the 24 hours endpoint.

The following observations could be made in the test vessels at the nominal pH 8 with a loading of 100 mg/L Dierbium trioxide:
- An average dissolved concentration of 255 ± 6 μg/L Er was found at the 24 hours endpoint with a between-vessel coefficient of variation of 2 % (N = 3) which met the <20 % quality criterion at the 24 hours endpoint. The within-vessel coefficients of variation met the <10 % quality criterion for all test vessels.
- Based on the specific surface area of the Dierbium trioxide powder (i.e. 0.6 m²/g test material, Annex 7), an erbium release per surface of 4.2 mg/m² was calculated at the 24 hours endpoint.
- Based on the erbium content of the test material (87.28 % Er) and the average dissolved erbium concentration, an erbium release of approximately 0.29 % could be calculated at the 24 hours endpoint.

Conclusions:

Under the conditions of this study at a loading of 100 mg/L, it was shown that an average concentration of 1486 μg/L Er (CVoverall = 5 %; N = 9) was measured at pH 6 (i.e. 1.7 % erbium release) and 255 μg/L Er (CVoverall = 2 %; N = 9) at pH 8 (i.e., 0.29 % erbium release), after 24 hours of exposure to the test medium at pH 6 and pH 8, respectively. Based on the rounded results, of the dissolved element concentrations, we may conclude that pH 6 is the pH where the highest concentrations of erbium were measured.

Executive summary:

The dissolution characteristics of the test material were investigated in accordance with the standardised guideline OECD 29, under GLP conditions.

The pH-dependent extent of dissolution of the test material was tested in standard aqueous solutions at pH 6 (0.5 % CO2-buffering) and pH 8 (air-buffering) for 24 hours at an agitation speed of 100 revolutions per minute (rpm). The extent of the transformation/dissolution was measured as the dissolved erbium concentrations obtained after 24 hours. Analyses of the concentrations of dissolved erbium and the determination of the total organic carbon content (TOC) of the test media were performed.

For the test at nominal pH 6 at a loading of 100 mg/L test material, an average dissolved concentration of 1486 ± 67 μg/L erbium (CVoverall = 5 %; N = 9) was found at the 24 hours endpoint. Based on the specific surface area of the Dierbium trioxide (i.e. 0.6 m²/g test material), this corresponds to an element release per surface of 25 mg/m² erbium. Based on the element content in the test material and the average dissolved element concentration in the test solution a release of erbium of 1.7 % of the content, could be calculated at the 24 hours endpoint in test medium at pH 6.

For the test at nominal pH 8 at a loading of 100 mg/L test material, an average dissolved concentration of 255 ± 6 μg/L erbium (CVoverall = 2 %; N = 9), was found at the 24 hours endpoint. Based on the specific surface area of the Dierbium trioxide (i.e. 0.6 m²/g test material), this corresponds to an element release per surface of 4.2 mg/m² erbium. Based on the element content in the test material and the average dissolved element concentration in the test solution a release of erbium of 0.29 % of the content, could be calculated at the 24 hours endpoint in test medium at pH 8.

The results can be assumed reliable since the test conditions stayed constant during the experiment.

Under the conditions of this study at a loading of 100 mg/L, it was shown that an average concentration of 1486 μg/L Er (CVoverall= 5 %; N = 9) was measured at pH 6 (i.e. 1.7 % erbium release) and 255 μg/L Er (CVoverall = 2 %; N = 9) at pH 8 (i.e., 0.29 % erbium release), after 24 hours of exposure to the test medium at pH 6 and pH 8, respectively.

Based on the rounded results, of the dissolved element concentrations, we may conclude that pH 6 is the pH where the highest concentrations of erbium were measured.

Description of key information

The test material has a water solubility of 0.0000128 g-mol/L (equating to 4.9 mg/L) at 29 °C and as such can be described as slightly soluble. 

Key value for chemical safety assessment

Water solubility:

4.9 mg/L

at the temperature of:

29 °C

Additional information

A value for the water solubility of the substance was obtained from a peer reviewed handbook. The data were awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch (1997). The water solubility of the test material was reported to be 0.0000128 g-mol/L at 29 °C (equating to 4.9 mg/L) and, as such, the substance can be described as slightly soluble. Further clarification regarding the units for water solubility can be found below.

Supporting information is available in the form of a company Material Safety Data Sheet. The test material was reported to be insoluble in water. Since no information was provided on materials and methods the data were assigned a reliability score of 4.

Further discussion regarding the quoted units for water solubility:

The substance dierbium trioxide has a RMM of 382.5169 g/mol and a quoted water solubility (Merck) of 1.28 x 10^-5 g-mol/L.

This equates to a water solubility of 4.9 mg/L according to the following rationale:

“g-mol/L” is a unit of molarity, i.e. the number of moles of a particular substance in a litre of solution.

Typically, molarity is written as mol/L, and it is understood that when converting to a mass-based solubility the calculation must be made using the molar mass in grams (as opposed to lb or any other non-metric unit). The “g” is not part of the units per se but merely confirms to the reader that this is a metric unit.

The use of “g” in the units in this case appears to be largely of historic relevance. Had the units been quoted as lb-mol/L, then in order to convert the mole-based solubility into a mass-based value, it would have been necessary to use the RMM for erbium oxide in the units of lb/mol.

The mass-based water solubility is therefore calculated by multiplying the molarity (1.28 x 10^-5 g-mol/L) by the molar mass in grams (382.5169 g/mol) to give 0.00490 g/L (4.9 mg/L).

Transformation/Dissolution Screening Study: ECTX bvba (2021)

The dissolution characteristics of the test material were investigated in accordance with the standardised guideline OECD 29, under GLP conditions.

The pH-dependent extent of dissolution of the test material was tested in standard aqueous solutions at pH 6 (0.5 % CO2-buffering) and pH 8 (air-buffering) for 24 hours at an agitation speed of 100 revolutions per minute (rpm). The extent of the transformation/dissolution was measured as the dissolved erbium concentrations obtained after 24 hours. Analyses of the concentrations of dissolved erbium and the determination of the total organic carbon content (TOC) of the test media were performed.

For the test at nominal pH 6 at a loading of 100 mg/L test material, an average dissolved concentration of 1486 ± 67 μg/L erbium (CVoverall = 5 %; N = 9) was found at the 24 hours endpoint. Based on the specific surface area of the Dierbium trioxide (i.e. 0.6 m²/g test material), this corresponds to an element release per surface of 25 mg/m² erbium. Based on the element content in the test material and the average dissolved element concentration in the test solution a release of erbium of 1.7 % of the content, could be calculated at the 24 hours endpoint in test medium at pH 6.

For the test at nominal pH 8 at a loading of 100 mg/L test material, an average dissolved concentration of 255 ± 6 μg/L erbium (CVoverall = 2 %; N = 9), was found at the 24 hours endpoint. Based on the specific surface area of the Dierbium trioxide (i.e. 0.6 m²/g test material), this corresponds to an element release per surface of 4.2 mg/m² erbium. Based on the element content in the test material and the average dissolved element concentration in the test solution a release of erbium of 0.29 % of the content, could be calculated at the 24 hours endpoint in test medium at pH 8.

The results can be assumed reliable since the test conditions stayed constant during the experiment.

Under the conditions of this study at a loading of 100 mg/L, it was shown that an average concentration of 1486 μg/L Er (CVoverall= 5 %; N = 9) was measured at pH 6 (i.e. 1.7 % erbium release) and 255 μg/L Er (CVoverall = 2 %; N = 9) at pH 8 (i.e., 0.29 % erbium release), after 24 hours of exposure to the test medium at pH 6 and pH 8, respectively.

Based on the rounded results, of the dissolved element concentrations, we may conclude that pH 6 is the pH where the highest concentrations of erbium were measured.