Carbohydrazide (CH₆N₄O) is a white, water-soluble crystalline solid primarily valued as a high-performance, low-toxicity oxygen scavenger for boiler water treatment. It serves as a safer alternative to hydrazine and offers several distinct performance and safety advantages.
Key Properties
Property Details
Chemical Name Carbohydrazide (also known as 1,3-Diaminourea, Carbonic dihydrazide)
CAS Number 497-18-7
Molecular Formula / Weight CH₆N₄O / ~90.08-90.11 g/mol
Appearance White crystalline powder or crystals
Solubility Very soluble in water; largely insoluble in organic solvents like alcohol and ether
pH (1% solution) ~7.4
Melting Point ~153-154°C (decomposes upon melting)
Density ~1.34 (25/4°C)
Reactivity Strong reducing agent. Incompatible with strong oxidizing agents, strong acids, copper, zinc, nickel, lead, and brass.
Primary Application: Oxygen Scavenger in Boiler Systems
Its main use is removing dissolved oxygen from feedwater to prevent corrosion in high-pressure boilers in power plants and other industries. It is highly effective, with confirmed oxygen scavenging properties under various conditions.
Key Advantages
Carbohydrazide is chosen over traditional options like hydrazine for several reasons:
Lower Toxicity: It presents a significantly lower health risk. Safety data suggests it is 5 to 30 times less acutely toxic than hydrazine, translating to easier handling and less stringent safety requirements.
Effective Metal Passivation: It does more than just remove oxygen; it also actively helps to passivate metal surfaces (reducing ferric oxide to ferrous oxide, for example), providing an additional layer of corrosion protection.
Favorable Decomposition Profile: It decomposes to volatile products (nitrogen, CO₂, and minimal ammonia), meaning it does not contribute to dissolved solids in the boiler system, which helps maintain water purity.
Proven Industry Adoption: It has been successfully adopted, having replaced hydrazine in about 20% of U.S. electric utility plants.
Thermal Stability: It is stable below 100°C (373K), allowing it to reach and protect the high-temperature boiler circuit effectively.
Additional Applications
Beyond water treatment, carbohydrazide is a useful chemical intermediate and reagent in organic synthesis and is used in:
Polymer Chemistry: As a curing agent for epoxide-type resins.
Pharmaceuticals & Agrochemicals: In the production of drugs, herbicides, and plant growth regulators.
Other Industries: As a component in textile cross-linking agents, color developer stabilizers in photography, and ammunition propellants.