Registration Dossier

Physical & Chemical properties

Melting point / freezing point

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

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).
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
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.
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.
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.

Key value for chemical safety assessment

Additional information