Difference Between Formaldehyde and Paraformaldehyde

Formaldehyde vs Paraformaldehyde

Formaldehyde is a basic organic chemical compound that can be made into different formulations. Paraformaldehyde is one such type, where it relies on the basic building blocks of formaldehyde but is different in structure. These varied formaldehyde formulations are commercially known in various terms and are used for different purposes depending on their properties.


Formaldehyde is a simple, organic, chemical compound that belongs to the functional group called ‘aldehydes’, hence the suffix. It is also the simplest form of the aldehyde present with the chemical formula CH2O or HCHO and is in gaseous state at room temperature. Formaldehyde gas is colourless and has a characteristic odour with a pungent nature.

Formaldehyde is industrially produced through the catalytic oxidation of methanol (CH3OH). Silver catalysts are generally used in this process. Being a simple organic compound, formaldehyde makes way as a starting material in a tremendous amount of organic reactions. It is also used in many industrially important polymerization reactions such as urea-formaldehyde resin, phenol-formaldehyde resin etc. Formaldehyde is also used in the production of varieties of plastics, fabric crease-resistants in the textile industry, component material for automobile engine systems etc. Dilute solutions of formaldehyde are also used as disinfectants and to preserve biological specimens. As mentioned above, formaldehyde shows a complicated nature as it adopts many different forms either by cyclization, polymerization or dissolution; however, it continues to show the same chemical characteristics as formaldehyde. Given all the benefits though, formaldehyde is known to be a human carcinogen and, in fact, is toxic to all animals as exposure to formaldehyde can cause serious health issues. Furthermore, solutions of formaldehyde show highly corrosive nature and formaldehyde can form extremely volatile/explosive compounds.


Paraformaldehyde is a polymerization product of formaldehyde. Polymers are bulky molecules made of many repeated unit molecules which are known as monomers. Ideally, polymerization is a process of reacting monomers which are the building blocks of the polymer, via a chemical reaction that binds the monomers together. Therefore, similarly about 8-10 units of formaldehyde (here formaldehyde acts as the monomer) polymerizes to form paraformaldehyde, which actually is the smallest unit among other possible secondary polymerizations. Formaldehyde is also called oxymethylene; hence paraformaldehyde is chemically referred to as ‘polyoxymethylene’. The word ‘poly’ generally means ‘many’.

Paraformaldehyde forms slowly when formaldehyde is in aqueous solutions and separates out as a white precipitate. During the preparation of saturated aqueous formaldehyde solutions also known as formalin, methanol and other stabilizers are often used to prevent this polymerization process. Paraformaldehyde easily de-polymerizes releasing formaldehyde gas upon dry heating, making paraformaldehyde a toxic agent. When de-polymerized, it can be used as disinfectants, fungicides and fixatives. When in polymer form it is used as a thermoplastic called ‘polyoxymethylene plastic’.

What is the difference between Formaldehyde and Paraformaldehyde?

• Formaldehyde is a simple organic chemical compound whereas paraformaldehyde is a polymer molecule.

• Formaldehyde has a strong and pungent odour, whereas paraformaldehyde only has a mild odour occurring due to the production of formaldehyde upon decomposing.

• Paraformaldehyde is a white precipitate at room temperature but formaldehyde is a gas.

• Paraformaldehyde is only one type of formaldehyde preparation hence has limited applications when compared to the many applications of formaldehyde.

• Paraformaldehyde is less toxic when compared to formaldehyde.