Reaction mass of disodium hexatitanium tridecaoxide and disodium trititanium heptaoxide

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:

2010-07-19 to 2010-08-31

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Remarks:

Only measured titanium solublity; fails to take into account possible dissociation/hydrolysis

Justification for type of information:

The water solubility was measured in deionised water by measuring dissolved titanium.
The method used will not detect potential dissociation / hydrolysis.
Disodium titanate substance (EC 234-802-9) has the molecular formula Na2TiO3 and its composition is expressed as (Na2O)x(TiO2), where x is ranging from 0.1 to 6 according to the SIP. This substance, Reaction mass of Disodium Hexatitanate and Sodium Metatitanate, has a value of x = 0.21, calculated from XRF results, has been identified as a mixture of two specific types of disodium titanate and is therefore within the scope of the disodium titanate SIP. It is assessed therefore that disodium titanate is an acceptable read-across substance for Reaction mass of Disodium Hexatitanate and Sodium Metatitanate

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)

Remarks:

signed, 2010-09-20

Type of method:

flask method

Remarks:

metal analysis via ICP-OES

Key result

Water solubility:

0.222 mg/L

Temp.:

20 °C

pH:

10.47

Method validation summary:

Method Principle:	Test mediumsamples delivered by eurofins-GAB GmbH (stabilized with nitric acid 65% (1 % v/v) at the test site) were used for analysis by ICP-OES without any further preparation. Final analysis was done by ICP-OES at titanium emission wavelengths of323.452 nm (quantification) and 338.376 nm (confirmation).
Specificity:	The concentrations of titanium in test medium samples were determined by ICP-OES at two emission wavelengths (quantification and confirmation). No significant interferences from the test medium matrix were detected at the emission wavelengths corresponding to titanium in any of the control specimens. The analytical method can therefore be regarded as highly specific for titanium.
Linearity:	The calibrationcurves used for titanium analysis at 323.452 nm were linear within the range from 0.0025 mg/L to 2.5 mg/L with a correlation coefficient of r = 1.0000 (r^2= 1.0000).
Precision (Repeatability):	At concentration levels of 0.115 mg/Ldisodium titanate(equivalent tomg/L titanium (LOQ)),mg/L disodium titanate (equivalent tomg/L titanium) and 2.3 mg/Ldisodium titanate(equivalent tomg/L titanium) the variation was ascertained by performing at least five determinations each in fortified test matrix. The relative standard deviations (at least five determinations each) were found to be 2.4 % at the 0.115mg/L, 2.5% at themg/L fortification level and 0.4 % at the 2.3 mg/L fortification level.
Accuracy (Recovery):	The accuracy is given as the recovery of titanium from test medium at three different concentration levels.The mean recoveries in the test medium ranged from 89 % to 100 % for titanium. The overall recovery was found to be 94% with a relative standard deviation of 5.1%.
Limit of Quantification:	The LOQ was defined at 0.115 mg/L regarding disodium titanate detection (0.05 mg/L regarding titanium).The limit of quantification (LOQ) was defined as the lowest fortification level with mean recoveries ranging from 70 % to 110 % at a relative standard deviation (RSD) of£ 20 % and blanks not exceeding 30 % of the LOQ. This requirement was fulfilled for the0.115mg/L test item (0.05 mg/L Ti) fortification level regarding titanium analysis in test medium.The limit of detection (LOD) was defined as 30 % of the limit of quantification (= 0.0345 mg/L regarding test item, 0.0150 mg/L

Results of the Flask Test:

The measurement of the samples taken from each bottle after 1 week plus 0 h, 24 h and 48 h and after 168 h, 192 h and 216 h were not used to determine the solubility because the results determined were not constant. Therefore the sampling procedure had to be modified twice as described.

The calculation from the content of titanium to the content of the test item based on the given titanium content of 43.5 %. In the following section single values are discussed. Due to rounding effects, presented values might slightly differ from values calculated manually.

Measured Titanium concentrations and pH in bidistilled water free from oxygen and carbon dioxide at 20 ± 0.5 °C: 

Time (1 week plus)	Sample No.	Titanium	Titanium (Mean)	Disodium titanate (Mean)	pH
[h]		[mg/L]	[mg/L]	[mg/L]
336	1	0.0843	0.091	0.209	10.48
	2	0.0976			10.46
360	1	0.0883	0.0984	0.226	10.51
	2	0.1085			10.44
384	1	0.1062	0.1005	0.231	10.47
	2	0.0947			10.47
	Mean:		0.097	0.222	10.47
	SD:		0.005	0.01	0.03
	RSD:		5.2	4.5	0.3

Conclusions:

Interpretation of results: slightly soluble (0.1-100 mg/L)
The water solubility of Disodium titanate in bidistilled water free from oxygen and carbon dioxide at 20 ± 0.5 °C is determined to be 0.222 mg/L (with a loading of 250 mg/L). The average pH of the saturated solution was pH 10.5.

Reference 2

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

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

Justification for type of information:

In-house testing to examine behaviour under acidic conditions to assess potential for dissociation or hydrolysis at low pH.

Reason / purpose for cross-reference:

reference to other study

Qualifier:

no guideline followed

Principles of method if other than guideline:

An experiment has been performed to mix the substance in distilled water and in molar HCl. After mixing for one hour at room temperature, the liquids were filtered and washed to leave a clear filtrate and residual solid on the filters. The filtrates were dried to determine if any soluble fractions and the solids formed from solution were weighed to give an approximate quantitative result.

GLP compliance:

no

Type of method:

other: Flask method with filtration

Key result

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

ca. 120 < mg/L

Element analysed:

Sodium (as 300 mg/l sodium chloride)

Loading of aqueous phase:

1 000 mg/L

Incubation duration:

1 h

Test conditions:

In molar HCl, ca ph 1 at 20 C

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

ca. 120 mg/L

Element analysed:

Sodium (as 200 mg sodium hydroxide)

Loading of aqueous phase:

1 000 mg/L

Incubation duration:

1 h

Test conditions:

In distilled water, at pH 10 at 20 C

Details on results:

Although the yield of dissolved salts was within exepcted parameters for the acid solution, there was an unexpectedly high yield in distilled water. The only explanation is that even under the natural alkaline conditions with the substance in non-buffered water, there is still some dissociation /hydrolysis.

The experiment to examine water soluble salts indicates that there is formation of soluble salts from mixing in excess acid or mixing in dilute forms in distilled water.

In terms of Na solubility, loading at 1000 mg/l resulted in ca 120 mg Na (300 mg NaCl) when mixed in acid and ca 120 mg Na (200 mg NaOH) in deionised water. It is assumed that a trace of Ti will have passed through filters, but with reported Ti solubility < 1 mg/l, this will be negligible.

Under both sets of conditions, sodium seems to dissociate to form soluble salts.

The proposed reaction scheme is:

 

Na₂O₃Ti + 2HCl      =          2NaCl + TiO₃H₂      =           TiO₂ + H₂O + 2NaCl

 

Theoretical yield of NaCl from 0.1 g sodium titanate (0.0007 moles) with excess 0.1 mole hydrochloric acid is ca 80 mg

                          

However, with metatitanate Na₂O₇Ti₃a lower yield of ca 30 mg NaCl is estimated

 

It is also noted from analysis (XRD) that the material tested contains a significant level of TiO2, therefore reducing apparent yield.

 

This experiment indicates that there is formation of soluble salts from mixing in excess acid or mixing in dilute forms in distilled water.

Conclusions:

The proposed reaction scheme is:

Na2O3Ti + 2HCl goes to 2NaCl + TiO3H2 which in turn hydrolyses to TiO2 + H2O + 2NaCl

Theoretical yield of NaCl from 0.1 g sodium titanate (0.0007 moles) with excess 0.1 mole hydrochloric acid is ca 80 mg
It is also noted from analysis (XRD) that the material tested contains a significant level of TiO2, therefore reducing apparent yield.

This experiment indicates that there is formation of soluble salts from mixing in excess acid or mixing in dilute forms in distilled water.

Executive summary:

The experiment to examine water soluble salts indicates that there is formation of soluble salts from mixing in excess acid or mixing in dilute forms in distilled water.

In terms of Na solubility, loading at 1000 mg/l resulted in ca 120 mg Na (300 mg NaCl) when mixed in acid and ca 120 mg Na (200 mg NaOH) in deionised water. It is assumed that a trace of Ti will have passed through filters, but with reported Ti solubility < 1 mg/l, this will be negligible.

Under both sets of conditions, sodium seems to dissociate to form soluble salts.

Description of key information

The test substance Disodium titanate is slightly soluble at 0.222 mg/L based on titantium in water.

However, as with all inorganic substances, solublity is based on dissociation and further work to look for presence of water soluble products of dissociation (eg sodium chloride) demonstrated a potential for dissociation and subsequent hydrolysis.

The proposed reaction scheme is:

Na2O3Ti + 2HCl goes to 2NaCl + TiO3H2 which in turn hydrolyses to TiO2  + H2O + 2NaCl

Theoretical yield of NaCl from 0.1 g sodium titanate (0.0007 moles) with excess 0.1 mole hydrochloric acid is ca 80 mg

It is also noted from analysis (XRD) that the material tested contains a significant level of TiO2, therefore reducing apparent yield.

This experiment indicates that there is formation of soluble salts from mixing in excess acid or mixing in dilute forms in distilled water.

Key value for chemical safety assessment

Water solubility:

0.222 mg/L

at the temperature of:

20 °C

Additional information

The experiment to examine water soluble salts indicates that there is formation of soluble salts from mixing in excess acid or mixing in dilute forms in distilled water.

In terms of Na solubility, loading at 1000 mg/l resulted in ca 120 mg Na (300 mg NaCl) when mixed in acid and ca 120 mg Na (200 mg NaOH) in deionised water. It is assumed that a trace of Ti will have passed through filters, but with reported Ti solubility < 1 mg/l, this will be negligible.

Under both sets of conditions, sodium seems to dissociate to form soluble salts.