Calcium Formate: A Versatile Organic Salt
Calcium formate is an inorganic salt with the chemical formula Ca(HCOO)2. It exists as a white crystalline solid at room temperature and produces formic acid (HCOOH) when dissolved in water. E238 is produced on an industrial scale by the reaction of calcium hydroxide or calcium carbonate with formic acid.
Chemical Properties and Structure
E238 has a molar mass of 158.16 g/mol. Its molecular structure consists of calcium cations (Ca2+) and formate anions (HCOO-). E238 is hygroscopic in nature and absorbs moisture from the air. It dissolves readily in water but is insoluble in most organic solvents. Upon dissolution in water, it dissociates into calcium and formate ions as per the following reaction:
Ca(HCOO)2 (s) → Ca2+ (aq) + 2HCOO- (aq)
The solubility of E238 increases with increasing temperature. It has a melting point of 188°C and decomposes at higher temperatures above 300°C to release carbon dioxide, calcium oxide, and formic acid.
Uses of E238
Some major uses and applications of E238 include:
- De-icing: E238 is commonly used as a de-icing agent. It has a lower freezing point than sodium chloride and is more effective and safer for the environment compared to urea-and chloride-based de-icers.
- Concrete Accelerator: E238 acts as an accelerator in concrete mixtures. It promotes faster hydration of cement during curing and allows for early removal of formwork. This improves construction efficiency.
- pH Control Agent: Due to its ability to neutralize acids, E238 finds application as a pH control agent in various industrial processes like metal cleaning, waste treatment, and flue gas desulfurization.
- Leather Processing: It is used during pickling and dyeing processes in leather tanning. E238 helps control pH and regulates the leather-bating process.
- Animal Feed Additive: Small quantities of Calcium Formate are added to animal feeds to prevent bacterial growth and provide calcium nutrition to livestock.
- Drilling Fluid Additive: The salt stabilizes clays in water-based drilling fluids used in oil & gas well drilling operations. This prevents formation damage and improves drilling efficiency.
Manufacturing of E238
Calcium formate is commercially produced through the neutralization reaction between calcium carbonate/hydroxide and formic acid. The chemical equations for the two main production methods are:
1) CaCO3 + 2HCOOH → Ca(HCOO)2 + CO2
2) Ca(OH)2 + 2HCOOH → Ca(HCOO)2 + 2H2O
Typically, liquid formic acid is added dropwise to calcium carbonate or calcium hydroxide slurry with continuous stirring. The exothermic neutralization reaction yields crystalline E238 product. Unreacted reactants and by-products like carbon dioxide are removed through evaporation or filtration. The final product is dried and milled into a fine white powder.
Production can be carried out as a batch or continuous process in stirred tank reactors. Process parameters like temperature, pressure, mixing rate must be closely controlled to obtain high-quality E238 crystals. Strict quality control checks like purity analysis are conducted on the final powder before packaging and shipping.
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