Sodium azide

Phototransformation in air

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in air

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

An aqueous sodium azide solution was evaporated on one side of a quartz tube. The tube was sealed on the vacuum line and heated for 24 hours at a temperature of 200 °C to remove water vapour.

GLP compliance:

no

Remarks:

GLP was not existing at the time of publication (1933).

Light source:

other: Mercury arc lamp

Light spectrum: wavelength in nm:

< 405

Details on test conditions:

No data

Reference substance:

not specified

Distance of source	1/D²	Rate of reaction	Aver. Rate	Rate × D²
12.2 cm	0.00672	2 and 3.5	2.75	409
19.35 cm	0.00267	0.96 and 1.03	0.995	373
22.65 cm	0.00195	0.65 and 0.71	0.68	354
33.50 cm	0.000891	0.31 and 0.32	0.315	353

 

The rate of decomposition with the light from the full mercury arc, was directly proportional to the intensity (see table).

Validity criteria fulfilled:

not applicable

Conclusions:

Sodium azide was found to decompose by light of wavelengths below 405 nm.

Executive summary:

Solid Sodium azide was found to be decomposed photochemically by wavelengths below approximately 405 nm. The rate of decomposition was directly proportional to the light intensity.

Reference 2

Endpoint:

phototransformation in air

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

secondary literature

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

no guideline followed

GLP compliance:

not specified

Light source:

other: high pressure mercury-arc lamp

Light spectrum: wavelength in nm:

254

Relative light intensity:

90

Quantum yield (for direct photolysis):

0

Validity criteria fulfilled:

no

Conclusions:

The quantum yield is only 0.001 using the full output of a high-pressure mercury arc lamp (254 nm). Therefore, direct photolysis is reported to have no influence on natural degradation of sodium azide.

Executive summary:

The quantum yield is only 0.001 using the full output of a high-pressure mercury arc lamp (254 nm). Therefore, direct photolysis is reported to have no influence on natural degradation of sodium azide.

Description of key information

According to Müller and Brous (1933), solid sodium azide was found to be decomposed photochemically by wavelengths below approximately 405 nm. The rate of decomposition was directly proportional to the light intensity. Regarding wavelength of 254 nm no photolysis is reported by Betterton (2003). A phototransformation within the troposphere is not expected.