Aluminium sulphate

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

not specified

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Remarks:

Data from a peer-reviewed handbook, accepted as a reliable data source according to Chapter R.7A of REACH Guidance on information requirements and chemical safety assessment, adequate for assessment. Restrictions apply as no experimental details and purity is not specified.

Principles of method if other than guideline:

unspecified

GLP compliance:

not specified

Water solubility:

ca. 313 g/L

Temp.:

0 °C

pH:

ca. 1.9 - ca. 2.4

Details on results:

pH ca. 1.9-2.4 at 1000 g/l and 25°C

Conclusions:

Interpretation of results (migrated information): very soluble (> 10000 mg/L)

Executive summary:

A reference handbook provides a water solubility of 313 g/L at 0°C for the anhydrous form of the substance.

Reference 2

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17/10/2014 to 24/10/2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Remarks:

Study following TDp method as laid down in GHS

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

Other quality assurance:

ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)

Type of method:

other: transformation/dissolution

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

7 471 µg/L

Element analysed:

result as µg Al/L

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

21.9°C, pH=4.75

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

359 µg/L

Element analysed:

result as µg Al/L

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

21.9°C, pH=5.27

Details on results:

The temperature of the test solutions fluctuated between 21.5 and 21.9°C which was in line with the test conditions of 20 – 23°C.
The test item has an immediate influence on the pH of the test systems. The pH measured in the medium at the start of the test, and in the blank and test item vessels during the test at pH 6 and pH 8 dropped from 6.05 to 4.75 and from 8.01 to 5.27, respectively. So, the measured data at pH 6 and at pH 8 were not within the specifications of ± 0.2.
The measured TOC of the media were <1.0 mg/L C, and below the required level of 2.0 mg/L C as laid down in the OECD Test Guidelines no.29
The test media at the start of the test and the blank control vessels during the test showed no concentrations above the reporting limit of 5 μg/L aluminium

Solution at pH6
When the test item and the test medium were mixed, the pH of the test medium decreased from pH 6.05 to 4.75 within a couple of minutes. The pH remained stable at about 4.75 during test and could not be corrected to pH 6.0 ± 0.2 by means of the used CO2/air buffer system within the 24 hours test period.
An average dissolved concentration of 7471 ± 16 μg/L Al was found at the 24 hours endpoint with a between-vessel coefficient of variation of 0%.
An average dissolved concentration of 7579 ± 46 μg/L Al was found at the 24 hours endpoint with a between-vessel coefficient of variation of 1% for samples which were centrifugated (30 minutes at 3000g) before 0.2 μm filtration.

Solution at pH8
When the test item and the test medium were mixed, the pH of the test medium decreased from pH 8.01 to 5.27 within a couple of minutes. The pH remained stable at about 5.27 during test and could not be corrected to pH 8.0 ± 0.2 by natural air buffering within the 24 hours test period.
An average dissolved concentration of 359 ± 37 μg/L Al was found at the 24 hours endpoint with a between-vessel coefficient of variation of 10%. The within-vessel coefficients of variation met the <10% quality criteria for all test vessels. Based on the aluminium content in the test item (8.8%, annex 7) and the average dissolved aluminium concentration, a remaining dissolved aluminium content of approximately 4.1% could be calculated at the 24 hours endpoint.
An average dissolved concentration of 346 ± 33 μg/L Al was found at the 24 hours endpoint with a between-vessel coefficient of variation of 9% for samples which were centrifugated (30 minutes at 3000g) before 0.2 μm filtration.

Executive summary:

During this study on Kemira ALG at a loading of 100 mg/L, it was shown that significant concentrations of aluminium 7471μg/L Al (CV=1%) at nominal pH 6 (actual pH was 4.75) and 359μg/L Al (CV=9%) at nominal pH 8 (actual pH was 5.27) were measured, using the standard protocol corresponding with a dissolved aluminium content of 85% and 4.1% respectively. However, it was not possible to maintain the pHs at the designated levels of 6 and 8 as the high concentration (100 mg/L) of the test substance used in the assay influenced the pH and the pH influenced the solubility.

Based on the rounded results, this study identified “pH 6” as the pH where the highest dissolved aluminium concentrations were found.

This dissolution result may be important in the design of the standard 7 days and/or 28 days transformation/dissolution test to enable appropriate hazard classification categories under EU-CLP and UN-Globally Harmonized System. Based on the results of this study a long term TDp study was performed at a more environmentally realistic concentration to reduce pH drift.

Reference 3

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17/10/2014 to 24/10/2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Remarks:

Study following TDp method as laid down in GHS

Reason / purpose for cross-reference:

reference to other 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

Qualifier:

according to guideline

Guideline:

other: GHS Annex 10

Deviations:

no

GLP compliance:

no

Other quality assurance:

ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)

Type of method:

other: transformation/dissolution

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

ca. 12 µg/L

Element analysed:

as Al2+

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

21.5°C, pH ca 6.0

Details on results:

The temperature of the test solutions fluctuated between 21.4 and 21.9°C which was in line with the test conditions of 20 – 23°C.
The pH measured in the medium at the start of the test, and in the blank and test item vessels during the test varied from 5.98 to 6.05. All measured data were within the specifications of pH 6 ± 0.2
The measured TOC of the media were <1.0 mg/L C, and below the required level of 2.0 mg/L C as laid down in the OECD Test Guidance no.29
The test media at the start of the test and the blank control vessels during the test showed no concentrations above the reporting limit of 5 μg/L aluminium
The dissolved oxygen concentration measured in the blank and test item vessels at pH 6 varied from 8.42 to 8.51 mg/L O2. These values were higher than the required value of ± 6 mg/L O2 at 22°C corresponding with a minimal saturation level in air of 70%.

1 mg/L loading			aluminium (µg/L Al)
	Time (h)		0	2	6	24	48	96	168	336	504	672
Accred. Report Limit			5	5	5	5	5	5	5	5	5	5
Detection limit			1	1	1	1	1	1	1	1	1	1
replica1	spl1		78	45	31	24	19	17	16	15	13	14
	spl2		75	45	31	24	19	17	17	14	14	14
	xavg,1		76	45	31	24	19	17	17	14	14	14
	swithin,1		2	0	0	0	0	0	0	0	0	0
	CVwithin,1(%)		2	0	0	1	0	2	1	2	1	0
	T (°C)								21.4			21.7
	pH								6.04			6.03
	DO (mg/L O2)								8.45			8.42
replica2	spl1		60	28	20	15	13	13	13	12	12	11
	spl2		59	30	20	16	13	14	13	12	12	11
	xavg,2		60	29	20	15	13	13	13	12	12	11
	swithin,2		1	1	1	0	0	1	0	0	0	0
	CVwithin,2(%)		1	4	3	3	3	4	0	1	1	1
	T (°C)								21.4			21.7
	pH								6.03			6.02
	DO (mg/L O2)								8.46			8.47
replica3	spl1		67	43	31	24	19	16	15	13	12	12
	spl2		69	47	30	29	19	16	15	13	12	12
	xavg,3		68	45	30	27	19	16	15	13	12	12
	swithin,3		1	3	1	4	0	0	0	0	0	0
	CVwithin,3(%)		2	7	3	15	1	1	2	0	1	1
	T (°C)								21.4			21.6
	pH								6.04			6.03
	DO (mg/L O2)								8.47			8.45
	xavg		68	40	27	22	17	16	16	13	12	12
	sbetween		8	9	6	6	3	2	2	1	1	1
	CVbetween(%)		12	24	23	27	19	13	12	9	8	11
	S		7	8	5	6	3	2	2	1	1	1
	CV (%)		11	21	20	25	17	11	11	8	7	10
xavg,v		within vessel averageof 2 samples where v is the replica blank control vessel number (N=2)
swithin,v		within vessel standard deviation where v is the replica blank control vessel number (N=2)
CVwithin,v		within vessel Coefficient of Variation where v is the replica blank control vessel number (N=2)
xavg		averageof 3 test vessels (2 samples per test vessel; blank corrected) (N=6)
sbetween		between vessel standard deviation (N=3)
CVbetween		between vessel Coefficient of Variation (N=3)
s		overall standard deviation (N=6)
CV		overall Coefficient of Variation (N=6)

Conclusions:

Interpretation of results (migrated information): insoluble (< 0.1 mg/L)
At a loading of 1 mg/L Kemira ALG using the modified ISO 6341 (OECD 203) standard medium at pH 6, an initial nominal concentration of 88 µg/L Al decreased to average values of 16 µg/L Al (CV=11%)and 12 µg/L Al (CV=10%) at the 7 days sample point and 28 days endpoint, respectively.

Executive summary:

The objective of this study was to obtain information about the dissolution characteristics of Kemira ALG, the product name for aluminium sulphate 14 -hydrate containing 9% (8.8 -9.2) elemental aluminium. The long-term (chronic) transformation/dissolution endpoint was based on the dissolved aluminium concentrations obtained after 28 days.With these results the sponsor is able to compare them with the chronic ecological reference value (ERV) at the corresponding pH of the element(s) tested in order to get information about the toxicity of the test item in aqueous medium and to classify the test item according to the EU-CLP and UN-Globally Harmonized System.

This study has been performed according to UN GHS Annex 10.

The set-up of this study, including the choice of the test system (modified ISO 6341 test medium at pH 6) was designed by the Study monitor on behalf of the Sponsor in order to obtain information about the dissolution characteristics (“removal from the water column”) and was based on the results of study X01-195 (24 hours Transformation/Dissolution Screening Study of Kemira ALG at a 100 mg/L loading in a standard aqueous medium at pH 6 and pH 8).

The pH-dependent extent of dissolution of Kemira ALG was tested in standard aqueous solutions at pH 6 (CO₂-buffering) for 28 days (1 mg/L loading) at an agitation speed of 100 rpm.

All test parameter conditions were fully in accordance with the GHS Annex 10 Test Guidance requirements:

·       The pH measured in the medium at the start of the test, and in the blank and test item vessels during the test varied from 5.98 to 6.05. All measured data were within the specifications of pH 6 ± 0.2.

·       The measured TOC of the media were <1.0 mg/L C, and below the required level of 2.0 mg/L C.

·       The temperature of the test solutions fluctuated between 21.4 and 21.9°C and corresponded to the required test conditions of 20 – 23°C.

·       The dissolved oxygen concentration measured in the blank and test item vessels at pH 6 varied from 8.42 to 8.51 mg/L O₂. These values were higher than the required value of ± 6 mg/L O₂at 22°C corresponding with a minimal saturation level in air of 70%.

The test medium and blank control were analysed for background aluminium concentrations over a 28 day study period and these were found to be negligible (close to or below limit of detection). At a loading of 1 mg/L Kemira ALG using the modified ISO 6341 (OECD 203) standard medium at pH 6, an initial nominal concentration of 88 µg/L Al decreased to average values of 16 µg/L Al (CV=11%)and 12 µg/L Al (CV=10%) at the 7 days sample point and 28 days endpoint, respectively. Based on the aluminium content in the test item (8.8%)and the average dissolved aluminium concentration in the test solutions, an aluminium recovery of 18% and 14% could be calculated at the7 days sampling point and 28 days extraction endpoint.

Reference 4

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

The experiment was not conducted according to guideline, and shows weakness regarding equilibration and separation of forms. However scientific reasoning was used and investigations regarding pH-dependency were considered suitable for purpose. Test substance is adequately characterised. Therefore the study is considered reliable with restrictions.

Principles of method if other than guideline:

Equilibration for 90 min, pH adjustment and measurement of dissolved aluminium.

Water solubility:

16 µg/L

Temp.:

20 °C

pH:

6

Remarks on result:

other: µg/L as Al; minimum solubility

Measured concentrations (as log) were plotted against pH, showing linear relationships below and above the minimum solubility.

Results match with the solubility calculated from the predicted species.

Conclusions:

Interpretation of results (migrated information): slightly soluble (0.1-100 mg/L)
Concentration of dissolved monomeric Al is related to speciation, and pH-dependent.

Executive summary:

Liquid alum (aluminium sulphate solution) was added to deionised water, and pH was adjusted between 4 and 9. After 90 min equilibration, and filtration to remove particulate and colloidal forms, dissolved Aluminium was measured by colorimetric method. Solubility was found to be pH-dependent, with speciation according to theoretical predictions. Minimum free (monomeric) aluminium was measured at pH=6.0 for deionised water with a concentration of 16 µg Al/L.

Reference 5

Endpoint:

water solubility

Type of information:

not specified

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Remarks:

Data from a secondary source, accepted as a reliable data source according to Chapter R.7A of REACH Guidance on information requirements and chemical safety assessment, adequate for assessment. Restrictions apply as no experimental details and purity is not specified.

Reason / purpose for cross-reference:

reference to other study

Principles of method if other than guideline:

unspecified

Remarks on result:

other: Soluble in 1 part water. (ref.1) supposed anhydrous form

Water solubility:

86.9 other: g / 100 mL water

Temp.:

0 °C

Remarks on result:

other: (ref.2) Aluminum Sulphate Octadecahydrate

Water solubility:

1 104 other: g / 100 mL water

Temp.:

100 °C

Remarks on result:

other: (ref.2) Aluminum Sulphate Octadecahydrate

For the anhydrous form, assuming that Soluble in 1 part water means 100g substance in 100 g water (= 100 mL), and considering a density of 1.61 as provided by the same source, this would correspond to 100 g in 100 + 100/1.61=162.1 mL = 617 g/L. Temperature is not specified.

For the octadecahydrate form, considering a density of 1.69 as provided by the same source, this would correspond to 574 g/L at 0°C and 1466 g/L at 100°C.

With MW of 666.4 g/mol and 342.1 g/mol for the octadecahydrate and the anhydrous forms respectively, this is equivalent to 295 and 753 g/L at 0 and 100°C respectively, expressed as anhydrous. The magnitude of order is consistent with the above data on the anhydrous form.

An estimation of solubility at 20°C can be calculated supposing concentration is a linear function of temperature; from the above, the relationship is [c] = 4.58 x T + 295. At 20°C, the interpolated concentration would therefore be ca 387 g/L (expressed as anhydrous).

Conclusions:

Interpretation of results (migrated information): very soluble (> 10000 mg/L)

Executive summary:

A reference database provides different water solubility values for both anhydrous and octadecahydrate forms. As the data were not expressed in standard unit, they were recalculated by the notifier to allow comparison with other data sources.

The substance is expected to have a solubility of ca 400 g/L at ambient temperature.

Reference 6

Endpoint:

water solubility

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

The test substance is aluminium sulphate basic, of formula Al2 (OH)0.16 (SO4)2.92, and not pure aluminium sulphate Al2 (SO4)3; however, according to the notifier, limited basicity may occur in the technical substance. Therefore, the chemical similarity (only 0.8% OH) is considered sufficient for supporting data on the hydrated form, the reference substance for the REACh registration dossier being the anhydrous form.

Reason / purpose for cross-reference:

read-across source

Water solubility:

> 1 000 g/L

Temp.:

20 °C

pH:

2.4

Executive summary:

From analogue, the water solubillity of the 15 - 16 H2O hydrated form is expected to be > 1000 g/L.

Reference 7

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

09 March 2010- 04 June 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

This study has been performed according to OECD and EC guidelines and according to GLP principles. Test substance is adequately characterised. Therefore full validation applies.

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Water solubility:

> 1 000 g/L

Temp.:

20 °C

pH:

2.4

Remarks on result:

other: Because the test substance is miscible with water in a 1:1 (w:v) ratio the main study was not performed.

Details on results:

Based on purity, this is equivalent to >543 g/L, expressed as anhydrous.

Conclusions:

Interpretation of results (migrated information): miscible
Totally dissolved at 1000 g/L, pH acidic.

Executive summary:

The water solubility of aluminium sulphate basic hydrated was investigated according to OECD/EC guidelines, flask method. A preliminary assay was conducted at the limit concentration of 1000 g/L. As the substance was totally dissolved, no main test was required.

Description of key information

Aluminium sulphate is a very soluble salt (>> 100 g/L), however aluminium speciation rapidly leads to salting out to various degrees which are highly pH dependent. Solubility of monomeric Al can descend as low as 16 µg Al/L within a 90 minute experiment in pure water, and 12 µg/L after 28 days in reconstituted natural medium.

Additional information

Numerous literature values are available, showing high solubility (between 300 and 600 g/L as eq. anhydrous form). However, while some of the selected data sources are considered reliable, experimental details are not available.

An experimental study, conducted with an analogue hydrated form, is also provided, and consistent with the above range.

Additionally, two valid transformation/dissolution studies were conducted, the first a 24 h study at nominal pH 6 and 8, in ISO 6341 reconstituted test medium 10x diluted (pH6) or undiluted (pH8), and aluminium concentrations dropped from 8.8 to 7.5 mg Al/L and 0.36 mg Al/L, respectively. This drop was less than expected due to the considerable reduction from the target pH (especially at pH6, which descended to 4.75 within a couple of minutes) caused by the capacity of aluminium to consume the alkalinity of the test medium (approximately 0.5 mg/L of alkalinity as CaCO3 per mg/L of alum according to Pernitsky and Edzwald, 2003). For this reason a 28 day TDp study was performed at a more environmentally realistic concentration of 1 mg/L at pH 6 (in diluted ISO 6341). In this case pH 6 was selected as the solubility was found to be the higher of the 2 pHs tested. In this study the original nominal concentration of 1 mg/L as aluminium sulphate (88 µg as elemental aluminium) dropped to 16 µg/L as elemental aluminium within 7 days and just 12 µg/L after 28 days and can therefore be considered as insoluble when added to environmental media within a few hours

A supporting publication reports consistent information on significant pH- and speciation-dependency, in deionised water, with a minimum solubility of 16 µg Al/L (pH = 6.0).

Moreover, in both experiments, solutions were filtered (0.2 µm) before analysis, in order to remove polymeric and colloidal species, as it is generally assumed that only dissolved metal ions will pass through such a filter.

This explains the variability between experiments observed.

Speciation is detailed under Section 5 on Environmental fate and pathways.