Registration Dossier
Registration Dossier
Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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.
Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 215-607-8 | CAS number: 1333-82-0
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- key study
- Justification for type of information:
- REPORTING FORMAT FOR THE ANALOGUE APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH and ANALOGUE APPROACH JUSTIFICATION
Based on reliable textbook data (HoWi, 2017) chromic(VI) oxide is soluble in water and forms immediately chromic acid, which is only known in solution:
CrO3 + H2O ---> H2CrO4
Based on this fact the dissociation properties of chromic acid have to be considered, as this is the species existing in water, not chromium(VI) oxide.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Please refer to the respective test item in the respective endpoint study record for details!
- Reason / purpose for cross-reference:
- read-across source
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- -0.61
- Remarks on result:
- other: Temperature not indicated, room temperature assumed
- No.:
- #2
- pKa:
- 6.488
- Remarks on result:
- other: Temperature not indicated, room temperature assumed
- Conclusions:
- When chromium(VI) oxide is dissolved in water it forms immediately chromic acid: CrO3+ H2O ---> H2CrO4
Chromic acid is only known in solution.
The chromic acid dissociates in water and is in the first stage strongly dissociated and in the second stage only weakly:
1) H2CrO4<==> H++ HCrO4-with pKa= -0.61
2) HCrO4-<==> H++ CrO42-with pKa= 6.488 - Executive summary:
Based on reliable textbook data (HoWi, 2017) chromic(VI) oxide is soluble in water and forms immediately chromic acid:
CrO3+ H2O ---> H2CrO4Chromic acid is only known in solution.
The chromic acid dissociates in water and is in the first stage strongly dissociated and in the second stage only weakly:
1) H2CrO4<==> H++ HCrO4-with pKa= -0.61
2) HCrO4-<==> H++ CrO42-with pKa= 6.488
Reference
When chromium(VI) oxide is dissolved in
water it forms immediately chromic acid:
CrO3+ H2O ---> H2CrO4
Chromic acid is only known in solution.
The chromic acid dissociates in water and is in the first stage strongly dissociated and in the second stage only weakly:
1) H2CrO4<==> H++ HCrO4-with pKa= -0.61
2) HCrO4-<==> H++ CrO42-with pKa= 6.488
Description of key information
Based on reliable textbook data (HoWi, 2017) chromic(VI) oxide is soluble in water and forms immediately chromic acid:
CrO3+ H2O ---> H2CrO4
Chromic acid is only known in solution.
The chromic acid dissociates in water and is in the first stage strongly dissociated and in the second stage only weakly:
1) H2CrO4<==> H++ HCrO4-with pKa= -0.61
2) HCrO4-<==> H++ CrO42-with pKa= 6.488
Key value for chemical safety assessment
- pKa at 20°C:
- -0.61
Additional information
Temperature is not stated in the key-value source, but room temperature is assumed. The test substance dissociates in a second step weakly, but for risk assessment the first dissociation step is of relevance based on a worst-case approach, as this first step is the reason for the acidic properties of the substance.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
