5-Chloro-2-Methyl-4-Isothiazolin-3-One [26172-55-4] is a technically defined substance with the molecular formula C4H4ClNOS and a molecular weight of 149.60. It exists as a clear light amber liquid with a density ranging from 1.256 to 1.296 g/mL at temperatures between 20-25 °C, exhibiting a viscosity of 11.4 cP at 25.7 °C. This compound carries a Warning signal word due to its potential acute toxicity when ingested and ability to cause allergic skin reactions.

• CAS Number: 26172-55-4
• Density: For a mixture of 5-chloro-2-methyl-3(2H)-isothiazolone and 2-methyl-3(2H)-isothiazolone: Clear light amber liquid; density: 1.256 - 1.296 g/mL at 20-25 °C; viscosity: 11.4 cP at 25.7 °C
• GHS Signal Word: Warning
• Molecular Weight: 149.60
• Exact Mass: 148.9702126
• Melting Point: 54-55 °C
• Molecular Formula: C4H4ClNOS
• Hazard Statements:
• H300: Fatal if swallowed [Danger Acute toxicity, oral]
• H317: May cause an allergic skin reaction [Warning Sensitization, Skin]