Sodium dithionite

Auto flammability

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

relative self-ignition temperature (solids)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-07-12 to 2010-07-27

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.16 (Relative Self-Ignition Temperature for Solids)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Recommendations on the Transport of Dangerous Goods: Manual of Tests and Criteria, 4th edition, 2003: Appendix 6 Screening Procedures, Division 4.2: Substances which may be liable to spontaneous combustion and Test N.4: Test for self-heating substances

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2010-08-25

Key result

Relative self-ignition temperature:

140 °C

The test item contains a residual moisture of 0.2 wt.-% which was determined by drying the test item under reduced pressure (approximately 100 mbar) at a temperature of 50°C.

In the investigation of the self-ignition behaviour in the Gewer-Oven for the pure test item and for the test item in mixture with Kieselguhr a self-ignition is detected starting at 160 °C. The maximum temperature was > 300 °C or > 250 °C for the pure test item or in mixture with Kieselguhr, respectively. For the pure test item a further multi-stage self-heating process was observed starting at 240 °C. Due to the fact, that the self-ignition temperature in the Grewer-Oven was below the limit of 220 °C the Bowes-Cameron-Cage Test (UN-Test N.4) had to be performed.

Table: Results on the screening test on self-ignition in the Gewer-Oven.

Experiment	Onset Self-ignition (°C)	Maximum temperature (°C)
Pure test item	160	>300
Test item in mixture with Kieselguhr (1:1)	160	>250

Bowes-Cameron-Cage Test (UN-Test N.4)

A) Test using a 100 mm cube sample (Weight in: 1.466 kg) at a oven temperature of 140 °C: The temperature in the centre of the sample reached a maximum temperature of > 500 °C already after 2.5 hours.

Due to a positive result in the 100 mm cube sample at an oven temperature of 140 °C a further test in the 25 mm cube sample at an oven temperature of 140 °C was performed.

B) Test using a 25 mm cube sample (Weight in: 17.3 g) at a oven temperature of 140 °C: The temperature in the centre of the sample reached a maximum temperature of > 300 °C already after 2 hours. Due to the positive result in the 25 mm cube sample at an oven temperature of 140 °C no further test had to be performed.

Conclusions:

The test item has to be assigned to Packaging group II of Division 4.2 according to the UN-Transport-regulation.
The test item has to be assigned to Category 1 for self-heating substances according to EC 1272/2008 (CLP-Guideline) Annex 1: 2.11. The substance has to be labelled with the Signal Word "Danger" and the Hazard Statement "H251: Self-heating, may catch fire".

Reference 2

Endpoint:

relative self-ignition temperature (solids)

Type of information:

other: Handbook data

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

no guideline followed

Principles of method if other than guideline:

Not applicable - Handbook data

GLP compliance:

no

Remarks on result:

other: please refer to `Any other information on results incl. table´

Combustible solid but not explosive. Burns slowly, about like sulfur.  Heats spontaneously in contact with moisture and air, and may ignite nearby combustible materials.

Conclusions:

Sodium dithionite is a combustible solid but not explosive. It burns slowly, about like sulfur. Heats spontaneously in contact with moisture and air, and may ignite nearby combustible materials.

Reference 3

Endpoint:

relative self-ignition temperature (solids)

Type of information:

experimental study

Adequacy of study:

supporting 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:

Not applicable- Publication

GLP compliance:

no

Remarks on result:

other: please refer to `Any other information on results incl. table´

Experimental results are presented which show how differences of approach to the determination of the ignition temperature of a dust layer can lead to widely  differing experimental values. For the material used, Sodium dithionite, experiments starting at a high temperature and working down lead to an apparent ignition temperature of nearly 400 °C, compared to a value of about 190 ° when experiments start at a low temperatures and work up. The cause of this behaviour is a 2-stage decomposition characteristic of Sodium dithionite.

Conclusions:

Experimental results are presented which show how differences of approach to the determination of the ignition temperature of a dust layer can lead to widely differing experimental values.
For the material used, Sodium dithionite, experiments starting at a high temperature and working down lead to an apparent ignition temperature of nearly 400 °C, compared to a value of about 190 ° when experiments start at a low temperatures and work up.
The cause of this behaviour is a 2-stage decomposition characteristic of Sodium dithionite.

Description of key information

A positive result is obtained in the test (UN-Test N.4) using the 25 mm cube sample at 140 °C.

Key value for chemical safety assessment

Autoflammability / Self-ignition temperature at 101 325 Pa:

140 °C

Additional information

For evaluation of this endpoint, data from an experimental study are used as key information. The study was conducted according to GLP and according to EU method A.16. Therefore, the test data are reliable without restrictions.

Self-ignition was determined in the Gewer-Oven and according to Bowes-Cameron-Cage Test (UN-Test N.4). Results indicate that the test item has to be assigned to Packaging group II of Division 4.2 according to the UN-Transport-regulation; and has to be assigned to Category 1 for self-heating substances according to EC 1272/2008 (CLP-Guideline) Annex 1: 2.11. The substance has to be labelled with the Signal Word "Danger" and the Hazard Statement "H251: Self-heating, may catch fire".

Two further references are available, providing supportive information:

Sodium dithionite is a combustible solid but not explosive. It burns slowly like sulfur and heats spontaneously in contact with moisture and air, and may ignite nearby combustible materials.

In experiments with sodium dithionite, ignition temperaturs of ca. 190 °C and ca. 400 °C are obtained. The cause of this behavior is a 2-stage decomposition characteristic of sodium dithionite. However, no details on test conditions are reported, so this experimental results are considered to be less significant.