Product Identification
【Product Name】5-Methyl-2,4-dihydro-pyrazol-3-one
【Synonyms】3-Methyl-5-oxo-2-pyrazoline；3-甲基吡唑-5-酮
【CAS】108-26-9
【Formula】C4H6N2O
【Molecular Weight】98.1
【EINECS】203-565-3
【RTECS】UQ9451500
【RTECS Class】Drug
【Beilstein/Gmelin】606503

Physical and Chemical Properties
【Appearance】Solid.
【Solubility in water】Very soluble
【Melting Point】221-224℃
【pKa/pKb】10.90 (pKb)

First Aid Measures
【Ingestion】If victim is conscious and alert, give 2-4 cupfuls of milk or water. Never give anything by mouth to an unconscious person. Get medical aid immediately.
【Inhalation】Remove from exposure to fresh air immediately. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical aid.
【Skin】Get medical aid. Flush skin with plenty of soap and water for at least 15 minutes while removing contaminated clothing and shoes. Wash clothing before reuse. Remove contaminated clothing and shoes.
【Eyes】Flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids. Get medical aid immediately.

Handling and Storage
【Storage】Keep container closed when not in use. Store in a tightly closed container. Store in a cool, dry, well-ventilated area away from incompatible substances.
【Handling】Wash thoroughly after handling. Remove contaminated clothing and wash before reuse. Use with adequate ventilation. Minimize dust generation and accumulation. Avoid contact with eyes, skin, and clothing. Keep container tightly closed. Avoid ingestion and inhalation.

Hazards Identification
【Ingestion】May cause irritation of the digestive tract. The toxicological properties of this substance have not been fully investigated.
【Inhalation】May cause respiratory tract irritation. The toxicological properties of this substance have not been fully investigated.
【Skin】May cause skin irritation.
【Eyes】May cause eye irritation.

Exposure Controls/Personal Protection
【Personal Protection】Eyes: Wear appropriate protective eyeglasses or chemical safety ggles as described by OSHA's eye and face protection regulations in 29 CFR 1910.133 or European Standard EN166. Skin: Wear appropriate protective gloves to prevent skin exposure. Clothing: Wear appropriate protective clothing to prevent skin exposure.
【Respirators】Follow the OSHA respirator regulations found in 29CFR 1910.134 or European Standard EN 149. Always use a NIOSH or European Standard EN 149 approved respirator when necessary.

Fire Fighting Measures
【Fire Fighting】Wear a self-contained breathing apparatus in pressure-demand, MSHA/NIOSH (approved or equivalent), and full protective gear. During a fire, irritating and highly toxic gases may be generated by thermal decomposition or combustion. To extinguish fire use water spray, dry chemical, carbon dioxide, or appropriate foam.

Accidental Release Measures
【Small spills/leaks】Clean up spills immediately, using the appropriate protective equipment. Sweep up or absorb material, then place into a suitable clean, dry, closed container for disposal. Avoid generating dusty conditions. Provide ventilation.

Stability and Reactivity
【Incompatibilities】Oxidizing agents.
【Stability】Stable under normal temperatures and pressures.
【Decomposition】Nitrogen oxides, irritating and toxic fumes and gases.