Silicic acid, calcium salt

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23/08/2010 - 28/09/2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

performed under GLP

Reason / purpose for cross-reference:

reference to same study

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

Principles of method if other than guideline:

No data

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Key result

Water solubility:

37 mg/L

Conc. based on:

other: Si analysis

Temp.:

20 °C

pH:

> 10 - < 10.3

Details on results:

For detailed results, see attached file "results.doc".
The test was carried out six times. The mean Ca-ion content dissolved was found to be 17.48 mg/L, and the mean Si-ion content dissolved was found to be 8.99 mg/L

Ca Content

Ca content was determined from the 507 mg/L of the test item solution in HCl conc. The solution was produced from 5.07 mg of the test item in 10 mL HCl conc. To 100 µL of this solution, 1000 µL HCl und 1000 µL KCl (10 % in water) were added, filled up to 100 mL with deionized water (dilution 1 : 1000) and measured Ca via AAS.

The data is presented in the following table:

 

Absorption	Ca conc. (diluted sample) mg/L	Dilution	Ca conc. (original sample) mg/L	Nominal conc. Test item mg/L	% Ca in Test Item
0.07029	0.0871	1000	87.1	507	17.19

 

Si Content

For the determination of Si content in the test item was used at first the measurements via UV-VIS was performed. The same stock solution (507 mg/L in HCl conc.) was used. Due to the presence of HCl conc. in the stock solution, the Si measurements were not successful. Therefore, Si content was calculated from the data of X-ray analysis as presented in the following table:

Parameter	Mr in g/mol	% in Oxide	% in Test Item
SiO2	60.0843	100.00%	47.30 %
Si	28.0855	46.74%	22.11%
O	15.9994

All replicates showed good correspondence. The concentration of the test item (related to Ca) was therefore calculated from the flask 1 – 6 and the Ca content of the test item (17.19 %) as 101.35 ± 5.85 mg/L, corresponding to the relative standard deviation 5.77 %. The measurements of the days 8, 9 and 13 (Flask 1) were included in the calculation of the mean since the differences between the measured concentrations lay below 15%.

Si measurement of the flask 1 showed a grate deviation from the other flasks and was not used for the calculation of the mean. The concentration of the test item (related to Si) was therefore calculated from the flask 2 – 6 and the Si content of the test item (22.11 %) as 36.97 ± 2.21 mg/L, corresponding to the relative standard deviation 5.97 %.

Accuracy measurements via standard addition showed a correlation r2 of 0.9978 (Ca content) and 0.9996 (Si content) indicating that matrix effects were insignificant.

Conclusions:

Interpretation of results (migrated information): decomposes
The water solubility (amount needed to saturate 1000 ml of deionised water) of crystalline calcium silicate hydrates (xonotlite - tobermorite) is 37 mg/L based on Si analysis.

Executive summary:

The water solubility of crystalline calcium silicate hydrates (xonotlite - tobermorite) was determined according to OECD guideline 105 using the shake flask method under GLP. The water solubility was found to be 100 mg/l at 20 °C based on Ca analysis and 37 mg/L based on Si analysis. As Ca-ions were also donated from a source other than the test material, the value obtained by Ca analysis is disregarded. The mean Ca-ion content dissolved was found to be 17.48 mg/L, and the mean Si-ion content dissolved was found to be 8.99 mg/L.

Description of key information

37 mg/l

Key value for chemical safety assessment

Water solubility:

37 mg/L

at the temperature of:

20 °C

Additional information

The water solubility of crystalline calcium silicate hydrates (xonotlite - tobermorite) was determined according to OECD guideline 105 using the shake flask method under GLP. As crystalline calcium silicate hydrates (xonotlite - tobermorite) decomposes when dissolved in water, the water solubility is expressed as the amount of test substance needed to saturate 1000 ml deionised water. The water solubility was found to be 100 mg/l at 20 °C based on Ca analysis and 37 mg/L based on Si analysis. As Ca-ions were also donated from a source other than the test material, the value obtained by Ca analysis is disregarded. The mean Ca-ion content dissolved was found to be 17.48 mg/L, and the mean Si-ion content dissolved was found to be 8.99 mg/L