Cyanuric acid

Melting point / freezing point

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Principles of method if other than guideline:

A combination of differential thermal analysis (DTA) with time-of-flight mass spectrometry and data storage on magnetic tape is used to study thermal decomposition of cyanuric acid.

GLP compliance:

not specified

Type of method:

thermal analysis

Melting / freezing pt.:

375 - 400 °C

Decomposition:

yes

Conclusions:

Based on the DTA (differential thermal analysis) data, CYA decomposes at 375-400°C. The decomposition is endothermic. Mass spectrometric analysis of the gaseous products identified isocyanic acid (HCNO, CAS 75-13-8) as the major product with some carbon monoxide (CO, CAS 630-08-0).

Reference 2

Endpoint:

melting point/freezing point

Type of information:

other: Handbook data

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Principles of method if other than guideline:

No method stated. Handbook data which provides result only

GLP compliance:

not specified

Melting / freezing pt.:

320 °C

Decomposition:

yes

Conclusions:

Cyanuric acid decomposes to cyanic acid at 320°C

Reference 3

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Principles of method if other than guideline:

The thermal decomposition of urea has been studied under flow reactor conditions using a differential scanning calorimeter (DSC) and Fourier transformed infrared spectroscopy (FT-IR). Biuret and cyanuric acid were decomposed in a separate set of experiments.

GLP compliance:

not specified

Melting / freezing pt.:

375 - 440 °C

Decomposition:

yes

Conclusions:

CYA decomposes at 375-440°C by differential scanning calorimetry (DSC). Fourier transform infrared (FT-IR) spectroscopy of the gaseous products confirmed production of isocyanic acid (HCNO, CAS 75-13-8). The temperature range found might have been lower and narrower if the temperature scanning rate was slower than the 20°C/min used.

Reference 4

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Principles of method if other than guideline:

A study was performed on the thermal decomposition of urea under open reaction vessel conditions by thermogravimetric analysis (TGA), HPLC, Fourier transform-infrared (FT-IR), and an ammonium ion-selective electrode (ISE). The thermal decomposition of urea produces cyanuric acid.

Type of method:

thermal analysis

Melting / freezing pt.:

320 - 375 °C

Decomposition:

yes

Decomp. temp.:

375 °C

.

Conclusions:

CYA decomposes to isocyanic acid (HCNO, CAS 75-13-8). Thermogravimetric analysis (TGA) showed minor decomposition at temperatures below 320°C. However, decomposition begins in earnest above 320°C and the decomposition rate increases with increasing temperature. Decomposition is complete by 375°C.

Reference 5

Endpoint:

melting point/freezing point

Type of information:

other: Handbook data

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Principles of method if other than guideline:

No method stated. Handbook data which provides results only

GLP compliance:

not specified

Melting / freezing pt.:

350 - 360 °C

Decomposition:

yes

Conclusions:

Cyanuric acid decomposes at 350-360°C to from gaseous isocyanic acid (HCNO, CAS 75-13-8) which can condense to re-form cyanuric acid when the gaseous HCNO is cooled.

Description of key information

Several sources of literature are available which give a melting point of cyanuric acid in the region of 320 - 440°C.