Potassium nitrate

Oxidising properties

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

oxidising solids

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: UN test O.1

Principles of method if other than guideline:

Test described in the United Nations Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, third revised edition, test O.1: Test for oxidizing solids (section 34.4.1). Also known as the conical pile test.

GLP compliance:

no

Key result

Sample tested:

1:1 sample-to-cellulose ratio

Parameter:

mean burning time

Result:

> 170 s

Remarks on result:

other: irregular and incomplete burning

Key result

Sample tested:

4:1 sample-to-cellulose ratio

Parameter:

mean burning time

Result:

140 s

Remarks on result:

other: incomplete burning

Key result

Sample tested:

reference: 3:7 mixture potassium bromate + cellulose

Parameter:

mean burning time

Result:

116 s

Key result

Sample tested:

reference: 2:3 mixture potassium bromate + cellulose

Parameter:

mean burning time

Result:

39 s

All test sample/cellulose mixtures exhibit burning times greater than those of all reference substance/cellulose mixtures. Based on the results of the investigation it was concluded that the investigated material do not have oxidizing properties in the sense of the criteria specified in the UN RTDG.

Interpretation of results:

other: No oxidizing properties according to the United Nations Recommendations on the Transport of Dangerous Goods.

Conclusions:

The test material (prills/granules) does not have oxidizing properties in the sense of the criteria specified in the United Nations Recommendations on the Transport of Dangerous Goods.

Reference 2

Endpoint:

oxidising solids

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2003

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Report contains a theoretical approach on oxidizing properties of potassium nitrate.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Two different methods exist for oxidizing properties
UN RTDG, Manual of Tests and Criteria, third revised revision, test O.1 (conical pile test). This method determined the dangerous properties of a substance as offered for transport. In case of a prilled fertilizer, the test is conducted on the prilled material.
The second method is the EC 92/69/EEC A.17 test. This method always determines the intrinsic dangerous properties of a material. Therefore, prilled fertilizers needs to be ground and sieved to a certain particle (125 µm) prior to testing.

GLP compliance:

not specified

Remarks on result:

not measured/tested

Remarks:

Conclusion based on theoretical approach

For transport purposes, prilled potassium nitrate is not an oxidizing substance when tested according to UN, but after grinding it to a powder, this material certainly has oxidising properties.

Conclusions:

Potassium nitrate (crystals) is a weak oxidizer. Potassium nitrate is not able to propagate a combustion. It cannot cause spontaneous ignition. Upon mixing or in contact with a combustible material, an ignition source is needed to initiate a fire. This fire will propagate faster than in a situation where only a combustible material is present. Potassium nitrate cannot deflagrate and is thermally stable. A dust explosion is not possible. In itself potassium nitrate does not pose a safety risk. This risk only exists when other dangerous substancs are present.

Reference 3

Endpoint:

oxidising solids

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Well documented study report. Test performed according to UN test O.1 by a trusted laboratory. Good description of the test material. No GLP.

Qualifier:

according to guideline

Guideline:

other: UN RTDG fourth revised edition, test O.1 (section 34.4.1)

Principles of method if other than guideline:

Test described in the United Nations Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, fourth revised edition, test O.1: Test for oxidizing solids (section 34.4.1). Also known as the conical pile test.

GLP compliance:

no

Sample tested:

reference: 3:7 mixture potassium bromate + cellulose

Parameter:

mean burning time

Result:

116 s

Remarks on result:

other: Minimum burning time: 108 s

Sample tested:

1:1 sample-to-cellulose ratio

Remarks:

NPP

Parameter:

mean burning time

Result:

141 s

Remarks on result:

other: Minimum burning time: 106 s

Sample tested:

1:1 sample-to-cellulose ratio

Remarks:

NPP-MJ

Parameter:

mean burning time

Result:

> 169 s

Remarks on result:

other: Minimum burning time: 150 s

Sample tested:

1:1 sample-to-cellulose ratio

Remarks:

NPP-TA

Parameter:

mean burning time

Result:

> 143 s

Remarks on result:

other: Minimum burning time: 90 s

Sample tested:

4:1 sample-to-cellulose ratio

Remarks:

NPP

Parameter:

mean burning time

Result:

67 s

Remarks on result:

other: Minimum burning time: 50 s

Sample tested:

4:1 sample-to-cellulose ratio

Remarks:

NPP-MJ

Parameter:

mean burning time

Result:

> 126 s

Remarks on result:

other: Minimum burning time: 73 s

Sample tested:

4:1 sample-to-cellulose ratio

Remarks:

NPP-TA

Parameter:

mean burning time

Result:

96 s

Remarks on result:

other: Minimum burning time: 54 s

The 1:1 mixtures exhibit an average burning time that is longer than the average burning time of the 3:7 reference mixtures. The 4:1 mixtures burn incompletely. At the end of the burning period, a considerable amount of sample is left unreacted. The mixture is not capable of reacting completely within the time limit indicated by the reference burning time.

NPP: Some sparks or minor flames are observed

NPP-MJ: only smouldering and very minor flames are observed

Interpretation of results:

other: no oxidising properties

Remarks:

>=98.8% of prills at >=0.85 mm

Conclusions:

Potassium nitrate Prills (granules >= 0.85 mm, anhydrous, >=98.8%): not oxidising.

Reference 4

Endpoint:

oxidising solids

Type of information:

other: RTDG

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Data from UN, considerd as a trusted source. UN numbers are assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods. They are published as part of their Recommendations on the Transport of Dangerous Goods, also known as the Orange Book. These recommendations are adopted by the regulatory organization responsible for the different modes of transport.

Reason / purpose for cross-reference:

reference to same study

Guideline:

other: not mentioned

Principles of method if other than guideline:

Method followed unknown. Transport classification is based on UN test O.1 of the UN-MTC, Part III, sub section 34.4.1 or on experience in the handling and use of the substance.

GLP compliance:

not specified

Sample tested:

other: not specified

Parameter:

other: not specified

Remarks on result:

other: Oxidising

Transported substances should be tested for oxidising properties and classified accordingly (Class 5.1). The results can be used for REACH purposes as well. UN1486: Hazard class 5.1 (oxidising substance); PGIII.

Interpretation of results:

other: Classified under UN1486: Hazard class 5.1 (oxidising substance)

Description of key information

Based on the transport classification, Class 5.1. O2. PG III, it was concluded that potassium nitrate crystals have oxidising properties.

Prilled potassium nitrate do not have oxidizing properties according to the outcome of the conical pile UN Test O.1 result.

Key value for chemical safety assessment

Oxidising properties:

yes

Additional information

Packaging group III equals CLP Category 3. 

The oxidising properties of a solid depend on its particle size and the composition: the smaller the particles, the higher the oxidising capacity. 

Article 9 from Regulation 1272/2008 allows manufacturers and importers to take into account the forms or physical states in which the substance is placed on the market and in which it can be reasonably be expected to be used when evaluating hazard information for classification. Based on this adequate, reliable and scientifically valid information for potassium nitrate prills and following Art. 9 of Regulation (EC) 1272/2008, potassium nitrate prills are not classified as oxidiser solids.

Justification for classification or non-classification

Based on the transport classification, potassium nitrate (crystals) has to be classified for the hazard 'Oxidising solid-Category 3' according to CLP Regulation (EC) No 1272/2008.

Based on the available information, prilled potassium nitrate does not have to be classified for the hazard 'Oxidising solid-Category 3' according to CLP Regulation (EC) No 1272/2008.