Potassium nitrate

Auto flammability

Administrative data

Endpoint:

auto-ignition temperature (liquids)

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Combining three handbook results, potassium nitrate could be described as a colourless crystalline solid or a white crystalline or granular powder.

Physical state at 20°C and 1013 hPa:

solid

-The CRC Handbook of Chemistry and Physics (80th ed.) describes potassium nitrate as colourless, rhombohedral crystals or powder.

-The Merck Index (12th ed.) describes potassium nitrate as colourless transparent prisms or a white granular or crystalline powder.

-Sax's Dangerous Properties of Industrial Materials (9th. ed.) describes potasium nitrate as transparent, colourless or white crystalline powder or orthorhombic crystals.

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Reference

Endpoint:

self-heating substances / mixtures

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
Nitrogen is in the highest oxidation state (+5) and will not react exothermic with any atom in the air. Potassium has a stable oxidation state (+1) and will not react with anything. Potassium nitrate is therefore concluded to be a stable non-flammable salt.

The substance has a wide-spread use and is not known as a self-heating substance.

On heating potassium nitrate melts without decomposition and the liquid is stable in air to at least 530°C. On further heating in air it decomposes into potassium nitrite (KNO2) and oxygen. Decomposition temperature: 650°C (from publication: High temperature properties and thermal decomposition of inorganic salts with oxyanions, Stern, K.H., CRC Press LLC, Boca Raton, 2001).

Additionally, the Ullman Encyclopedia (see the attachment) contains a chapter on nitrates that describes in particular the uses of potassium and sodium nitrates in high temperature applications, and in particular in solar technology, which implies that they are stable at those temperatures in the long term. Please refer to section 1.5 of the attachment stating the use of potassium/sodium nitrate in high temperature applications.

Nitrates are also used in the production of glass, a process that take place at very high temperatures.