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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

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Administrative data

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Endpoint:
dissociation constant
Type of information:
other: Literature value
Adequacy of study:
weight of evidence
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Principles of method if other than guideline:
No data
GLP compliance:
not specified
Dissociating properties:
no
No.:
#1
pKa:
4.8
Temp.:
20 °C

The stated temperature of 20 °C is not given in the text but is the common temperature for dissocation temperature measurement. Also the OECD guideline 112 (dissocation constant) proposes this temperature

Conclusions:
The dissociation constant of sodium azide is 4.8.
Executive summary:

The dissociation constant of sodium azide is 4.8.

Endpoint:
dissociation constant
Type of information:
other: Literature value
Adequacy of study:
weight of evidence
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Principles of method if other than guideline:
The substance is dissolved in water before addition of a slight excess of sulphuric acid. The hydrazoic acid is then distilled off to give the sodium salt of hydrazoic acid. The conductivity of the water is then measured using Kohlrausch's method, by means of induction currents.
GLP compliance:
not specified
Dissociating properties:
not determined
No.:
#1
pKa:
4.8
Temp.:
25 °C
Remarks on result:
other: K is calculated as 0.0000166
Conclusions:
The dissociation constant of hydrazoic acid is 4.8.
Executive summary:

Based on measurements of conductivity taken using Kohlrausch's method, the k value of hydrazoic acid is 0.0000166. Therefore, the pK value is 4.8.

Endpoint:
dissociation constant
Type of information:
other: Literature value
Adequacy of study:
key study
Study period:
not available
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Principles of method if other than guideline:
not available
GLP compliance:
not specified
Dissociating properties:
yes
No.:
#1
pKa:
4.7
Temp.:
20 °C
Conclusions:
The substance sodium azide has a pKb of 9.3 at 20 °C.
Executive summary:

The substance sodium azide has a pKb of 9.3 at 20 °C.

Description of key information

According to published data, the substance Sodium Azide has a pKa of 4.7 to 4.8 at 20 °C. 

Key value for chemical safety assessment

pKa at 20°C:
4.75

Additional information