Registration Dossier

Data platform availability banner - registered substances factsheets

Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Dissociation constant

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Sep. 10, 2019 - Feb. 20, 2020; experimental phase: Sep. 18-19, 2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 112 (Dissociation Constants in Water)
Version / remarks:
1981-05-12
Deviations:
yes
Remarks:
The test item solution was membrane filtrated. This can be considered as uncritical, as the test item contains insoluble parts which must be removed before the measurement and without this treatment a measurement is not possible.
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Name: Silicic acid, magnesium aluminium sodium salt
Batch no.: 201810LC007
Appearance: white fluffy powder
Composition: Sodium; Magnesium; Aluminium; Silica
CAS No.: 12040-43-6
EC-No.: 234-919-5
Purity: >95%
Homogeneity: homogeneous
Production date: October 2018
Expiry date: Nov. 2020
Specific surface area: 57.9 m²/g
Dissociating properties:
no
Remarks:
the majority of SMAS is present in non-dissociated form
No.:
#1
pKa:
ca. 9.161 - ca. 9.249
Temp.:
20 °C
No.:
#2
pKa:
ca. 7.405 - ca. 7.519
Temp.:
20 °C
No.:
#3
pKa:
ca. 6.143 - ca. 6.485
Temp.:
20 °C

Above values are the means of three independent determinations ± their standard deviations

Six Main Tests were performed. The first Main Test and the second Main Test were not taken into account for evaluation.

The measurement of the third Main Test, fifth Main test and sixth Main Test were used for evaluation and calculation (see chapter 7.2). Main Test four was not used as the deviation at EQP 3 was too high.

The pKb1 was calculated as 4.795 ± 0.044

The pKb2 was calculated as 6.538 ± 0.057

The pKb3 was calculated as 7.686 ± 0.171

These values are also the means of three independent determinations ± their standard deviations

Conclusions:
Results of this study are stated as follow:

The pKa1 was calculated as 9.205 ± 0.044
The pKa2 was calculated as 7.462 ± 0.057
The pKa3 was calculated as 6.314 ± 0.171
and
The pKb1 was calculated as 4.795 ± 0.044
The pKb2 was calculated as 6.538 ± 0.057
The pKb3 was calculated as 7.686 ± 0.171
These values are the means of three independent determinations ± their standard deviations
Executive summary:

This study was performed in order to determine the dissociation constant of Silicic acid, magnesium aluminium sodium salt.

Description of key information

The pKa1 was calculated as 9.205 ± 0.044

The pKa2 was calculated as 7.462 ± 0.057

The pKa3 was calculated as 6.314 ± 0.171

and

The pKb1 was calculated as 4.795 ± 0.044

The pKb2 was calculated as 6.538 ± 0.057

The pKb3 was calculated as 7.686 ± 0.171

These values are the means of three independent determinations ± their standard deviations

Key value for chemical safety assessment

pKa at 20°C:
7.66

Additional information

The key value stated above is the mean of pKa1, pKa2 and PKa3 without their standard deviations.