UN3077 is assigned to sodium formate due to its classification as an environmental hazard under the UN Model Regulations for the Transport of Dangerous Goods. Below is a detailed description of its chemical and physical properties, along with relevant safety and transport considerations:
Chemical Properties
1.Molecular Formula:
2.1.\(\text{NaHCO}_2\) or \(\text{HCOONa}\)
2.Molecular Weight: 68.01 g/mol
3.Chemical Structure:
4.1.Composed of a sodium cation (\(\text{Na}^+\)) and a formate anion (\(\text{HCOO}^-\)), forming an ionic bond.
2.The formate ion is the conjugate base of formic acid (\(\text{HCOOH}\)), making sodium formate a weak base in aqueous solution.
5.Acidity/Basicity:
6.1.pH in Water: A 1% aqueous solution has a pH of ~8.5–9.5 (alkaline), as the formate ion hydrolyzes slightly:\(\text{HCOO}^- + \text{H}_2\text{O} \rightleftharpoons \text{HCOOH} + \text{OH}^-\)
7.Reactivity:
8.1.Acid Reaction: Reacts with strong acids (e.g., \(\text{HCl}, \text{H}_2\text{SO}_4\)) to release formic acid:\(\text{HCOONa} + \text{HCl} \rightarrow \text{NaCl} + \text{HCOOH}\)
2.Heat Sensitivity: Decomposes at high temperatures (\(>300^\circ\text{C}\)) to produce sodium oxalate, sodium carbonate, and carbon monoxide (CO):\(2\text{HCOONa} \xrightarrow{\Delta} \text{Na}_2\text{C}_2\text{O}_4 + \text{H}_2\uparrow\) (Note: Inadequate heating may also generate CO, a toxic gas.)
3.Redox Reactions: Acts as a reducing agent in some organic syntheses (e.g., formylation reactions).
9.Solubility:
10.1.Highly soluble in water (\(\sim 100 \, \text{g/100 mL at 20^\circ\text{C}\)).
2.Sparingly soluble in organic solvents like ethanol; insoluble in ether.
11.Stability:
12.1.Stable under normal conditions, but hygroscopic (absorbs moisture from air), forming aqueous solutions over time.
2.Avoid contact with strong oxidizing agents, acids, or moisture-sensitive compounds.
Physical Properties
|
Property |
Description |
|
Appearance |
White crystalline powder or granules; odorless or slightly acetic acid-like. |
|
Odor |
Virtually odorless; may have a faint smell of formic acid when moist. |
|
Melting Point |
~253°C (decomposes rather than melts; transitions to a liquid-like state). |
|
Boiling Point |
Not applicable (decomposes before boiling). |
|
Density |
~1.92 g/cm³ (solid). |
|
Vapor Pressure |
Negligible at room temperature. |
|
Hygroscopicity |
Highly hygroscopic; absorbs water to form hydrated crystals (e.g., \(\text{HCOONa} \cdot 2\text{H}_2\text{O}\)). |
|
pH (1% Aqueous Solution) |
8.5–9.5 (alkaline, as noted earlier). |
|
Electrical Conductivity |
Aqueous solutions are good conductors due to ion dissociation (\(\text{Na}^+\) and \(\text{HCOO}^-\)). |
UN3077 Classification and Safety
UN Number: UN3077
Hazard Class: Environmentally Hazardous Substance (Category 9 under UN regulations).
Risk Statements (GHS):
H302: Harmful if swallowed.
H315: Causes skin irritation.
H319: Causes serious eye irritation.
H410: Very toxic to aquatic life with long-lasting effects.
Safety Measures:
PPE: Use gloves (e.g., nitrile), safety goggles, and lab coats to avoid skin/eye contact.
Storage: Store in tightly sealed containers in a dry, ventilated area, away from acids and oxidizers.
Spill Handling: Collect spills with absorbent materials; avoid washing into drains (risk to waterways).
Transport Considerations (UN3077)
Packaging Groups: Not specifically assigned (Category 9 hazards often use generic packaging).
Labeling: Requires an Environmentally Hazardous Substance label during transport.
Regulations: Compliant with ADR/RID (Europe), TDG (Canada), and DOT (USA) for international shipping.
Environmental Impact: Avoid release into soil, water, or air; formate is biodegradable but can cause oxygen depletion in aquatic systems at high concentrations.
Key Differences from Other Salts
Compared to sodium acetate (\(\text{CH}_3\text{COONa}\)), sodium formate is more hygroscopic and has a stronger tendency to act as a reducing agent.
Its alkaline pH and formate ion make it unique for applications requiring both buffering and mild reduction capabilities.
Understanding these properties is critical for safe handling, regulatory compliance, and optimizing its use in industrial processes.
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