Chemical Properties
Clear liquid
Chemical Properties
Formaldehyde is an important chemical widely used by industry to manufacture building materials and numerous household products. It is also a by-product of combustion and certain other natural processes. It is present in substantial concentrations both indoors and outdoors. Formaldehyde is well known as a preservative in medical laboratories, as an embalming fl uid, and as a sterilizer. Its primary use is in the production of resins and as a chemical intermediate. Urea formaldehyde (uf) and phenol formaldehyde (pf) resins are used in foam insulations, as adhesives in the production of particle board and plywood, and in the treating of textiles. Sources of formaldehyde in the home include building materials, smoking, household products, and the use of unvented, fuel-burning appliances, like gas stoves or kerosene space heaters. Formaldehyde, by itself or in combination with other chemicals, serves a number of purposes in manufactured products. It has been reported that the use and production of formaldehyde in 1998 was about 11.3 billion pounds and the international production crossed over 46 billion pounds in 2004.
Definition
ChEBI: The simplest aldehyde.
Reactivity Profile
FORMALDEHYDE, SOLUTION, reacts violently with strong oxidizing agents (hydrogen peroxide, performic acid, perchloric acid in the presence of aniline, potassium permanganate, nitromethane). Reacts with bases (sodium hydroxide, potassium hydroxide, ammonia), and with nitrogen dioxide (explosive reaction around 180°C). Reacts with hydrochloric acid to form highly toxic bis(chloromethyl) ether. Polymerization reaction with phenol may develop sudden destructive pressure [Bretherick, 5th ed., 1995, p.168].
Air & Water Reactions
The solution gives up formaldehyde vapors readily. These vapors are flammable over a wide vapor-air concentration range. Water soluble.
Hazard
Moderate fire risk. Explosive limits in air 7–
73%. Toxic by inhalation, strong irritant, a carcinogen. (Solution) Avoid breathing vapor and avoid
skin contact. Confirmed carcinogen.
Health Hazard
Formaldehyde is a colorless, pungent-smelling gas. Exposures to low levels of formaldehyde cause irritation of the eyes, nose, throat, skin, nausea, and diffi culty in breathing. Short-term exposure to formaldehyde can be fatal. Long-term exposure to low levels of formaldehyde may cause respiratory diffi culty, eczema, and sensitization. Occupational workers with asthma have been found to be more sensitive to the effects of inhaled formaldehyde; in high concentrations, formaldehyde triggers attacks in people with asthma. Also, intake/drinking large amounts of formaldehyde causes severe pain, vomiting, and coma leading to death. Acute and chronic health effects of formaldehyde vary depending on the individual. The typical threshold for development of acute symptoms due to inhaled formaldehyde is 800 ppb; however, sensitive individuals have reported symptoms at formaldehyde levels around 100 ppb.
Health Hazard
The probable oral lethal dose for humans is 0.5-5 g/kg, or between 1 ounce and 1 pint for a 150 pound person. Acute--below 1 ppm, odor perceptible to most. 2-3 ppm, mild tingling of eyes. 4-5 ppm, increased discomfort, mild lacrimation. 10 ppm, profuse lacrimation; can be withstood only for few minutes. 10-20 ppm, breathing difficult, cough, severe burning of nose and throat. 50-100 ppm, acute irritation of respiratory tract, very serious injury likely. Skin--primary irritation from strong solutions, gas. Delayed--sensitization dermatitis. Suspected carcinogen. Effects in women include menstrual disorders and secondary sterility. Solutions splashed in eyes have caused injuries ranging from severe, permanent corneal opacification and loss of vision to minor discomfort. In people sensitized to formaldehyde, late asthmatic reactions may be provoked by brief exposures at approximately 3 ppm.
Potential Exposure
Formaldehyde has found wide indus trial usage as a fungicide, germicide; and in disinfectants
and embalming fluids. It is also used in the manufacture of
artificial silk and textiles, latex, phenol, urea, thiourea and
melamine resins; dyes, and inks; cellulose esters and other
organic molecules; mirrors, and explosives. It is also used
in the paper, photographic, and furniture industries. It is an
intermediate in drug manufacture and is a pesticide
intermediate.
Fire Hazard
Toxic vapors such as carbon dioxide and carbon monoxide are generated during combustion. Explosion hazard: when aqueous formaldehyde solutions are heated above their flash points, a potential for explosion hazard exists. High formaldehyde concentration or methanol content lowers flash point. Reacts with nitrogen oxides at about 180; the reaction becomes explosive. Also reacts violently with perchloric acid-aniline, performic acid, nitromethane, magnesium carbonate, and hydrogen peroxide. When heated, irritant formaldehyde gas evolved from solution. The main products of decomposition are carbon monoxide and hydrogen. Metals such as platinum, copper, chromia, and alumina also catalyze the formation of methanol, methylformate, formic acid, carbon dioxide, and methane. Reacts with peroxide, nitrogen oxide, and performic acid causing explosions. Can react with hydrogen chloride or other inorganic chlorides to form bis-chloromethylether (BCME), a known carcinogen. Very reactive, combines readily with many substances, 40% solution is powerful reducing agent. Incompatible with amines, azo compounds, dithiocarbamates, alkali and alkaline earth metals, nitrides, nitro compounds, unsaturated aliphatics and sulfides, organic peroxides, oxidizing agents, and reducing agents. Aqueous solutions are unstable. Commercial formaldehyde-alcohol solutions are stable. Gas is stable in absence of water. Avoid oxidizing and alkaline materials. Hazardous polymerization may occur. Compound will polymerize with active organic materials such as phenol. Will polymerize violently in the presence of caustics and nitrides; (amines) exothermic reaction, (Azo compound) exothermic reaction giving off nitrogen gas, (caustics) heat generation and violent polymerization, (dithiocarbamates) formation of flammable gases and toxic fumes, formation of carbon disulfide may result, (alkali and alkaline earth metals) heat generation and formation of a flammable hydrogen gas.
First aid
If this chemical gets into the eyes, remove any
contact lenses at once and irrigate immediately for at least
30 minutes, occasionally lifting upper and lower lids. Seek
medical attention immediately. If this chemical contacts the
skin, remove contaminated clothing and wash immediately
with soap and water. Seek medical attention immediately.
If this chemical has been inhaled, remove from exposure,
begin rescue breathing (using universal precautions, includ ing resuscitation mask) if breathing has stopped and CPR if
heart action has stopped. Transfer promptly to a medical
facility. When this chemical has been swallowed, get medi cal attention. Give large quantities of water and induce
vomiting. Do not make an unconscious person vomit.
Medical observation is recommended for 24 to 48 hours
after breathing overexposure, as pulmonary edema may be
delayed. As first aid for pulmonary edema, a qualified med ical professional might consider administering a corticoste roid spray. Cigarette smoking may exacerbate pulmonary
injury and should be discouraged for at least 72 hours
following exposure. If symptoms develop or overexposure
is suspected, chest X-ray should be considered.
Shipping
UN1198 Formaldehyde solutions, flammable,
Hazard Class: 3; Labels: 3-Flammable liquid, 8-Corrosive
material. Cylinders must be transported in a secure upright
position, in a well-ventilated truck. Protect cylinder and
labels from physical damage. The owner of the compressed
gas cylinder is the only entity allowed by federal law
(49CFR) to transport and refill them. It is a violation of
transportation regulations to refill compressed gas cylinders
without the express written permission of the owner.
UN2209 Formaldehyde solutions, with not<25% formal dehyde, Hazard class: 8; Labels: 8-Corrosive material.
UN3077 For solids containing varying amounts of formal dehyde : UN3077
Environmentally hazardous substances, solid, n.o.s., Hazard
class: 9; Labels: 9-Miscellaneous hazardous material,
Technical Name Required.
Incompatibilities
Pure formaldehyde may polymerize
unless properly inhibited (usually with methanol). May
form explosive mixture with air. Incompatible with strong
acids; amines, strong oxidizers; alkaline materials; nitrogen
dioxide; performic acid; phenols, urea. Reaction with
hydrochloric acid forms bis-chloromethyl ether, a carcino gen. Formalin is incompatible with strong oxidizers, alkalis,
acids, phenols, urea, oxides, isocyanates, caustics,
anhydrides.
Description
Formaldehyde is a colorless, flammable gas with a distinctive pungent odor. It is the simplest
aldehyde, which is a class of organic compounds with the carbonyl group bonded to at
least one hydrogen atom. Formaldehyde was described by August Wilhelm von Hoff mann
(1818–1892) in 1867 after the Russian Aleksandr Butlerov (1828–1886) had inadvertently
synthesized it in 1857. Formaldehyde readily dissolves in water to produce a solution called
formalin, which is commonly marketed as a 37% solution.
Waste Disposal
Return refillable compressed
gas cylinders to supplier. Incineration in solution of combus tible solvent. Consult with environmental regulatory agen cies for guidance on acceptable disposal practices. Generators
of waste containing this contaminant (≥100 kg/mo)
must conform with EPA regulations governing storage, trans portation, treatment, and waste disposal.
Physical properties
Formaldehyde is a clear, colorless liquid with a pungent, suffocating odor. Burning taste. Experimentally determined odor threshold concentrations of 1.0 ppmv and 0.50 ppmv were reported by Leonardos et al. (1969) and Nagata and Takeuchi (1990), respectively. Also,formalin is an aqueous solution that is 37% formaldehyde by weight; inhibited solutions (added to prevent polymeri zation) usually contain 6 12% methyl alcohol. Formaldehyde is used in the manufacture of plastics and resins by reaction with phenols,urea, and melamine. It is used as a preservative,a disinfectant, and as a chemical intermediate.
History
Formaldehyde is a by-product of combustion of organic compounds, metabolism, and
other natural processes. Formaldehyde results from wood combustion and elevated atmospheric
concentrations can result from forest fires, as well as from urban pollution sources
such as transportation. Formaldehyde has been identified as a significant indoor air pollutant.
Building materials such as particleboard, plywood, and paneling are major sources of formaldehyde
because they incorporate formaldehyde resins as bonding adhesives. Other sources of
formaldehyde in the home are carpets, upholstery, drapes, tobacco smoke, and indoor combustion
products. Formaldehyde may be emitted from building materials for several years after
installation. In the two decades of the 1960s and 1970s, a half million homes in the United
States used urea formaldehyde foam insulation, but health complaints led to its elimination
as an insulator in the early 1980s. People react differently to formaldehyde exposure, but it is
estimated that between 10% and 20% of the population will experience some reaction at concentrations
as low as 0.2 parts per million. Formaldehyde irritates the eyes, nose, and throats,
producing coughing, sneezing, runny nose, and burning eyes. More severe reactions result in insomnia, headaches, rashes, and breathing difficulties. Some states have established indoor air
quality standards ranging from 0.05 to 0.5 ppm.
Preparation
Formalin is adjusted to pH 8 and urea is added to give a urea to
formaldehyde ratio of about 1 :2.5 molar. The resulting solution is boiled
under reflux for 1 hour. Butanol (1.5-2.0 mole per mole of urea) is then added
together with a little xylene. The latter forms, with butanol and water, a
ternary azeotrope which on distillation yields a condensate separating into an
upper organic layer and a lower aqueous layer. By discarding the lower layer
and returning the upper layer to the reactor, water is progressively removed
from the system. After a substantial proportion of the water has been
removed, an acid catalyst (e.g. phosphoric acid or phthalic anhydride) is
added and heating is continued. When the required degree of reaction is
attained, the solution is neutralized and concentrated to the desired solids
content.
Production Methods
The industrial preparation of formaldehyde has occurred since the late 1800s and involvesthe catalytic oxidation of methanol: 2CH3OH(g) + O2(g) → 2CH2O(g).the oxidationtakes place at temperatures between 400°C and 700°C in the presence of metal catalysts. Metalsinclude silver, copper, molybdenum, platinum, and alloys of these metals. Formaldehyde iscommonly used as an aqueous solution called formalin. Commercial formalin solutions varybetween 37% and 50% formaldehyde. When formalin is prepared, it must be heated anda methanol must be added to prevent polymerization; the final formalin solution containsbetween 5% and 15% alcohol.
Flammability and Explosibility
Formaldehyde gas is extremely flammable; formalin solution is a combustible liquid (NFPA rating = 2 for 37% formaldehyde (15% methanol), NFPA rating = 4 for 37% formaldehyde (methanol free)). Toxic vapors may be given off in a fire. Carbon dioxide or dry chemical extinguishers should be used to fight formaldehyde fires.
Chemical Reactivity
Reactivity with Water No reaction; Reactivity with Common Materials: No reactions; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Not pertinent; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent.
Agricultural Uses
Microbiocide, Fungicide, Bactericide; Soil
sterilent: Registered for use in the U.S. Not approved for
use in EU countries. Formaldehyde has found wide
industrial usage as a fungicide, germicide and in disinfectants. It is used most often in an aqueous solution
stabilized with methanol (formalin). It is also a pesticide
intermediate.
Trade name
DYNOFORM®; FANNOFORM®;
FORMALITH®; FORMOL®; FYDE®; HERCULES
37 M6-8®; HOCH®; IVALON®; KARSAN®;
LYSOFORM®; MAGNIFLOC 156C FLOCCULANT®;
MORBICID®; STERIFORM®; SUPERLYSOFORM®
Biochem/physiol Actions
Formaldehyde is the simplest aldehyde that denatures the bihelical regions of RNA and converts the polynucleotides into random coils. It is a genotoxic substance that significantly induces DNA-protein crosslinks (DPC), sister-chromatid exchanges, micronuclei formation and leads to cytotoxicity. It also induces tumors in the nasal epithelium of rats and supposed to be a human carcinogen.
Carcinogenicity
Formaldehyde is known to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in humans and supporting data on mechanisms of carcinogenesis. Formaldehyde was first listed in the Second Annual Report on Carcinogens in 1981 as reasonably anticipated to be a human carcinogen based on sufficient evidence from studies in experimental animals. Since that time, additional cancer studies in humans have been published, and the listing status was changed to known to be a human carcinogen in the Twelfth Report on Carcinogens (2011).
Source
Formaldehyde naturally occurs in jimsonweed, pears, black currant, horsemint, sago
cycas seeds (1,640 to 2,200 ppm), oats, beets, and wild bergamot (Duke, 1992).
Formaldehyde was formed when acetaldehyde in the presence of oxygen was subjected to
continuous irradiation (λ >2200 ?) at room temperature (Johnston and Heicklen, 1964).
Schauer et al. (2001) measured organic compound emission rates for volatile organic
compounds, gas-phase semi-volatile organic compounds, and particle phase organic compounds
from the residential (fireplace) combustion of pine, oak, and eucalyptus. The gas-phase emission
rates of formaldehyde were 1,165 mg/kg of pine burned, 759 mg/kg of oak burned, and 599 mg/kg
of eucalyptus burned.
Gas-phase tailpipe emission rates from California Phase II reformulated gasoline-powered
automobiles with and without catalytic converters were 8.69 and 884 mg/km, respectively
(Schauer et al., 2002).
Environmental Fate
Biological. Biodegradation products reported include formic acid and ethanol, each of which can further degrade to carbon dioxide (Verschueren, 1983).
Photolytic. Major products reported from the photooxidation of formaldehyde with nitrogen oxides are carbon monoxide, carbon dioxide and hydrogen peroxide (Altshuller, 1983). In synthetic air, photolysis of formaldehyde gave hydrochloric acid and
Irradiation of gaseous formaldehyde containing an excess of nitrogen dioxide over chlorine yielded ozone, carbon monoxide, nitrogen pentoxide, nitryl chloride, nitric acid and hydrochloric acid. Peroxynitric acid was the major photolysis product when chlo
Chemical/Physical. Oxidizes in air to formic acid (Hartley and Kidd, 1987). Trioxymethylene may precipitate under cold temperatures (Sax, 1984). Polymerizes easily (Windholz et al., 1983). Anticipated products from the reaction of formaldehyde with ozone orhydroxyl radicals in air are carbon monoxide and carbon dioxide (Cupitt, 1980). Major products reported from the photooxidation of formaldehyde with nitrogen oxides are carbon monoxide, carbon dioxide and hydrogen peroxide (Altshuller, 1983).
Reacts with hydrochloric acid in moist air forming bis(chloromethyl)ether. This compound may also form from an acidic solution containing chloride ion and formaldehyde (Frankel et al., 1974). In an aqueous solution at 25°C, nearly all the formaldehyde add
storage
work with formaldehyde should be conducted in a fume hood to prevent exposure by inhalation, and splash goggles and impermeable gloves should be worn at all times to prevent eye and skin contact. Formaldehyde should be used only in areas free of ignition sources. Containers of formaldehyde should be stored in secondary containers in areas separate from oxidizers and bases.
Purification Methods
It commonly contains added MeOH. Add KOH solution (1 mole KOH: 100 moles HCHO) to ~37% by weight aqueous formaldehyde solution (formalin), or evaporate to dryness, to give paraformaldehyde polymer which, after washing with water, is dried in a vacuum desiccator over P2O5 or H2SO4. Formaldehyde is regenerated by heating the paraformaldehyde to 120o under vacuum, or by decomposing it with barium peroxide. The monomer, a colourless flammable gas, is passed through a glass-wool filter cooled to -48o in a CaCl2/ice mixture to remove particles of polymer, then dried by passage over P2O5 and either condensed in a bulb immersed in liquid nitrogen or absorbed in ice-cold conductivity water. The gas or aqueous solutions have pungent suffocating odours, are LACHRYMATORY and suspected carcinogens, handle carefully. Formalin is a disinfectant and a preservative of dead animal and plant tissues. [Beilstein 1 IV 3017.]
Toxicity evaluation
The carbonyl atom is the electrophilic site of formaldehyde,
making it react easily with nucleophilic sites on cell membranes
and in body fluids and tissues such as the amino groups in
protein and DNA. Higher concentrations of formaldehyde
precipitate protein. It is probable that formaldehyde toxicity
occurs when intracellular levels saturate formaldehyde dehydrogenase
activity, allowing the unmetabolized intact molecule
to exert its effects locally. Formaldehyde is a very strong crosslinking
agent even in the low concentration range. The reaction
mechanism of this agent is the initial addition of formaldehyde
to a primary amine on either an amino acid residue or DNA
base to yield a hydroxymethyl intermediate. Then the hydroxymethyl
group condenses with a second primary amine to yield
a methylene bridge.