2-amino-6-methyl-1,2,4-triazolo[1,5-a]pyrimidin-5(1H)-one

Endpoint summary

Description of key information

The test substance is a beige powder with no noticeable odour and a density of 1.56 x 10³kg/m³. The melting temperature of the test substance was determined to be 321.3 °C (594.5 K) and the substance decomposed upon melting. Therefore, due to thermal decomposition upon melting, a definitive boiling temperature was not determined. The vapour pressure of the test substance was determined using the gas saturation method to be < 5.0 x 10^-6Pa at 20 °C and 25 °C. The water solubility of the substance was found to be pH dependent, with a solubility of 1.1 g/Lat pH 5 and a solubility of 13 g/L at pH 7.7, at 20 °C. Also the octanol-water partition coefficient was found to be pH dependent and decreasing with increasing pH value. The log Kow was - 0.6 at pH 5, -0.97 at pH 7 and -2.6 at pH 9. The surface tension of the test substance in water was determined according to the ring method to be 72.7 mN/m at 20.0 ± 0.5 °C. The particle size distribution of the test substance was initially determined by sieve analysis; the percentage of test substance having an inhalable particle size of less than 100 µm was determined to be 79.8%. Too few particles were of a size less than 10.0 μm to allow accurate assessment of the mass median aerodynamic diameter. By cascade impactor analysis, the percentage of test item having a thoracic particle size of less than 10.0 µm and respirable particle size of less than 5.5 µm was determined to be 4.1% and 1.3% respectively. The pH of a 1% w/v aqueous dispersion of the test substance was determined to be 4.6 at 25 ºC (mean of 2 determinations). The test substance does not meet the GHS criteria to be classified as explosive, oxidising or flammable. A safety study performed to the appropriate UN test also showed that the test substance does not have any pyrophoric, self heating or self-reactive properties and does not evolve flammable gases on contact with water.