Registration Dossier
Registration Dossier
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EC number: 200-821-6 | CAS number: 74-90-8
Dissociation constant
Administrative data
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 1962
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: This study is similar to, but precedes the development of OECD Guideline 112.
Data source
Reference
- Reference Type:
- publication
- Title:
- Thermodynamics of Metal-Cyanide Coordination I. pK, ∆Ho and ∆So values as a function of temperature for hydrocyanic acid dissociation in aqueous solution
- Author:
- Izatt RM, JJ Christensen, RT Pack, R Bench
- Year:
- 1 962
- Bibliographic source:
- Inorganic Chemistry 1: 828-831
Materials and methods
Test guideline
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 112 (Dissociation Constants in Water)
- Deviations:
- yes
- Remarks:
- precedes guideline
- GLP compliance:
- no
Test material
- Reference substance name:
- Hydrogen cyanide
- EC Number:
- 200-821-6
- EC Name:
- Hydrogen cyanide
- Cas Number:
- 74-90-8
- Molecular formula:
- CHN
- IUPAC Name:
- hydrogen cyanide
- Details on test material:
- Stock HCN solution was prepared by passing a 0.05 F NaCN solution through an Amberlite GC-120, Type 1 ion exchange column until the Na concentration as determined by a flame test was less than 0.05% of that originally present.
Constituent 1
Results and discussion
- Dissociating properties:
- yes
Dissociation constant
- No.:
- #1
- pKa:
- ca. 9.36
- Temp.:
- 20 °C
- Remarks on result:
- other: 95 % Confidence Limit ± 0.012
Applicant's summary and conclusion
- Conclusions:
- The pKa of hydrocyanic acid is 9.36 at 20°C and 9.11 at 30°C.
- Executive summary:
The pKa of hydrocyanic acid is 9.36 at 20 °C.The predominant speciation of all inorganic cyanide in the body is HCN due to this weak acid dissociation constant.
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