Formaldehyde and Formalin


Formaldehyde is a derivative of the aliphatic aldehyde substances and its chemical formula is HCHO or CH2O. It can be produced from the oxidation of methyl alcohol and oxygen by using copper or silver as a catalyst.

At normal pressure, formaldehyde is a combustible and colorless gas with a pungent odor that provides heat at 4.4 kcal / g when it is ignited. If can be explosive when combined with air and oxygen. Commercially, it is used in the form of solution in water that contains formaldehyde at a concentration of about 37-50% by weight.

• IUPAC name : Methanal
• Common name :
– Formaldehyde
– Methylene Oxide
– Oxomethylene
– Oxymethylene
– Methylaldehyde
• Common name of solution :
– Formalin
– Formal
– Formaldehyde

Formaldehyde has chemical properties that are different from those of general aldehyde compounds since it has only one hydrogen atom attaching on aldehyde group (-CHO) and has no alkyl radicals within its molecule so it is a substance that is easily susceptible to reaction with other substances.


Formaldehyde solution in an unstable solution that will be changed as formic acid at all times especially at high-temperature storage. Storage at low temperatures can help reduce the incidence of acids, but there is a disadvantage that causes sedimentation followed. Therefore, a stabilizer, such as 10-15% methanol by weight, must be added so that formaldehyde solution or formalin can be stored at low-temperature storage.

Paraformaldehyde is a polymer type of formaldehyde and its structural formula is (CH2O)nH2O. It is known as paraform or polyxymethylene. It is a white powder and well soluble in water but insoluble in organic solvents. It can easily react and break down as formaldehyde especially when heated and in acidity or alkalinity. When combined with hot paraffin, paraformaldehyde will release formaldehyde gas and react according to the equation below. This gas can be used to kill germs.

• Formaldehyde (nHCHO)        →      Paraformaldehyde (HCHO)n

• Paraformaldehyde (CH2OCH2OCH2OCH2O-)     →   Heat   →    Formaldehyde (CH2O)

• Formalin (HCHO + H2O-)     →   Heat   →    Formaldehyde (CH2O)

Sources and production
1. Formaldehyde can be formed by natural process in the troposphere by means of the oxidation of hydrocarbon compounds in which OH radicals and ozone react to each other to become formaldehyde.

2. Formaldehyde can be formed by industrial process by oxidizing methanol in two ways:
• Oxidizing methanol by using copper and silver as a catalyst at 600-720 ºC as shown in the equation.

2CH3OH  + O2     →   Heat+Silver   →    2HCHO + 2H2O

• Oxidizing methanol by using iron molybdenum oxides as a catalyst at 270-380 ºC.

Formalin is a chemical substance commonly used as a component of disinfection solutions, a cleansing agent in the paper, textile and paint industries, and used to maintain the physical conditions of dead animals or corpses.

Formalin, which is commonly used, is a substance prepared from mixing formaldehyde with water at a concentration of formaldehyde of about 37-50% by weight and often including methanol of about 10-15%. It is well soluble in water and can be combined as polymer when they more concentrated. However, the combination of formaldehyde is reduced by the addition of methanol. For example, mixing 37% formaldehyde with 7% methanol makes the solution stable at 21 ºC, while mixing 37% formaldehyde with 1% methanol makes the solution stable at 40.5 ºC, but 37% formaldehyde without being mixed with methanol causes the solution to be stable at 67-71 ºC.

Benefits of Formaldehyde and Formalin
1. Industrial benefits
• Production of resins and plastics
• Production urotropins, alcohol, drugs, paints and explosives
• Catalyst in paint adhesion and dying agent
• Bleaching process
• Production of paints and printing inks
• Production of slipping and waterproof papers
• Component of metals and prevention of oxidation
• Production of powders used in synthetic silks to help improve weight and hardness of silks
• Extension of photo shelf life
• Component of antiseptic solutions and disinfectants

2. Agricultural benefits
• Destruction and prevention of germs in soil, water, plants and animals
• Extension of shelf life of fruits, vegetables and meatso there are often news on the detection of formalin mixed in meat foods, such as pork, chicken, fish, shrimps, and squids
• Prevention of damage during transport of agricultural products
• Cleaning and sterilization of school equipment and buildings
• Production of fertilizers

3. Medical benefits
• Destruction and prevention of medical equipment and instruments
• Preservation of dead bodies and animals

4. Cosmetic products
• Component of cosmetics to prevent excessive sweating
• Component of toothpastes, mouthwashes, soaps and shaving creams and disinfectant
• Component of body deodorants


• Acute toxicity: Experimental injections of formaldehyde to the mice showed an initial symptom of panic followed by drowsiness, fatigue, shortness of breath and death in 2-3 hours.
• Chronic toxicity : Experiments of giving formaldehyde to dogs and rabbits via foods at 2-50 mg / kg of body weight for 129 days found that these animals were weighted down, their red blood cells and hemoglobin in the blood were fewer, some of them died. Autopsies found a change in the tissue characteristics of their digestive systems, such as stomach, intestines and liver.
• Physical toxicity : When the body gets 5% formaldehyde in 100 cc of water of 100 cc will cause irritation in the gastrointestinal tract, vomiting, bleeding in the stomach and intestines, and death within 40 days. Inhalation or ingestion of formaldehyde in low concentrations can cause headache and lacrimation.
• Chronic physical toxicity : When getting formaldehyde continuously, especially in those working on this substance, there will be symptoms related to the gastrointestinal tract and respiratory system, such as disorder of respiratory and gastrointestinal system or gastrointestinal inflammation.
• Toxicity from contact : Acute symptoms include skinredness, inflammation, blisters, swells and scales, while chronic symptoms include darker and itchy skins.

Levels of toxicity
1. Concentration of 1 ppm can perceive its smell.
2. Concentration of 2-3 ppm causes irritation of respiratory system.
3. Concentration of 4-5 ppm causes lacrimation and irritation of respiratory system.
4. Concentration of 10 ppm causes contiguous lacrimation and irritation of respiratory system.
5. Concentration of 10-20 ppm causes lacrimation and severe irritation of respiratory system, including a burning sensation on the neck, difficulty breathing, coughing and severe illness.
6. Concentration of 50-100 ppm causes same as 10-20 ppm, but severe more than.