Disodium disilicate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June 2009

Reliability:

1 (reliable without restriction)

Reason / purpose for cross-reference:

reference to other study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Company data. No guideline indicated. For details on method see IUCLID6 materials and methods section.

GLP compliance:

no

Remarks:

Company data.

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
not indicated

Radiolabelling:

no

Analytical monitoring:

not required

Details on sampling:

10 g disodium disilicate (delta-crystalline) in 100 ml water were stirred for 5 days at 30°C and then stored in a drying oven at 30°C over the weekend. Subsequently the solution was further stirred for 3 days at 30°C. Afterwords the solution was filtered through a 0.2 µm membrane filter. The filtrate was evaporated at 90°C and the residue was dried at 200°C until constant weight. The undissolved product was dried at approx. 70°C for 2 h.

Buffers:

not applicable

Estimation method (if used):

not applicable

Details on test conditions:

A saturated solution of disodium disilicate (delta-crystalline) in water was prepared. After filtration of the undissolved material the aqueous solution was evaporated to dryness and subsequently dried at 200°C. The crystalline modification of the dry residue was analysed by powder diffratometry. The results of disodium disilicate (delta-crystalline) were compared with commercial available amorphous sodium disilicate.

Duration:

10 d

pH:

7

Temp.:

30 °C

Initial conc. measured:

104 g/L

Number of replicates:

1

Positive controls:

no

Negative controls:

no

Statistical methods:

not applicable

Preliminary study:

no preliminary study

Test performance:

no remarks on test performance

Transformation products:

yes

No.:

#1

No.:

#1

Details on hydrolysis and appearance of transformation product(s):

The powder diffractogram of the dissolved and subsequently dried disodium disilicate (delta-crystalline) doesn't show any crystalline structures but only signals of amorphous silicate. The SiO2/Na2O ratio of the dried material is comparable to the composition of commercial available amorphous sodium disilicate. Therefore, it can be concluded that the crystalline structure of layered delta-sodium disilicate is completely destroyed by dissolution in water yielding an aqueous solution which is identical to a solution of amorphous sodium disilicate (CAS No. 1344-09-8).

Remarks on result:

not measured/tested

Other kinetic parameters:

not applicable

Details on results:

not indicated

Validity criteria fulfilled:

not applicable

Conclusions:

It can be concluded that the crystalline structure of disodium disilicate (delta-crystalline) is completely destroyed by dissolution in water yielding an aqueous solution which is identical to a solution of amorphous sodium disilicate (CAS No. 1344-09-8).

Executive summary:

The powder diffractogram of the dissolved and subsequently dried disodium disilicate (delta-crystalline) doesn't show any crystalline structures but only signals of amorphous silicate. The SiO2/Na2O ratio of the dried material is comparable to the composition of commercial available amorphous sodium disilicate. Therefore it can be concluded that the crystalline structure of layered delta-sodium disilicate is completely destroyed by dissolution in water yielding an aqueous solution which is identical to a solution of amorphous sodium disilicate (CAS No. 1344-09-8).

Upon dilution of concentrated commercial amorphous sodium silicate solutions with water, the highly cross-linked polysilicate ions depolymerize rapidly to monosilicate ions. The resulting water glass is identical to naturally occuring silicate. Thus, it can be concluded that disodium disilicate (delta-crystalline) is degraded hydrolytically to a naturally occuring substance, which is widespred in nature.

Description of key information

Based on the present study and basic textbook knowledge it can be concluded that the crystalline structure of disodium disilicate (delta-crystalline) is destroyed by dissolution in water yielding an aqueous solution which is identical to a solution of amorphous sodium disilicate (CAS No. 1344-09-8).

Additional information

The powder diffractogram of the dissolved and subsequently dried disodium disilicate (delta-crystalline) doesn't show any chrystalline structures but only signals of amorphous silicate. The SiO2/Na2O ratio of the dried material is comparable to the composition of commercial available amorphous sodium disilicate. Therefore it can be concluded that the crystalline structure of layered delta-sodium disilicate is completely destroyed by dissolution in water yielding an aqueous solution which is identical to a solution of amorphous sodium disilicate (CAS No. 1344-09-8).

Upon dilution of concentrated commercial amorphous sodium silicate solutions with water, the highly cross-linked polysilicate ions depolymerize rapidly to monosilicate ions. The resulting water glass is identical to naturally occuring silicate. Thus, it can be concluded that disodium disilicate (delta-crystalline) is degraded hydrolytically to a naturally occurring substance, which is widespread in nature.