Small encyclopedia of chemical material - Formaldehyde

Small encyclopedia of chemical material - Formaldehyde

History

Formaldehyde was first reported in 1859 by the Russian chemist Aleksandr Butlerov (1828–86),and was conclusively identified in 1869 by August Wilhelm von Hofmann.

Occurrence

Processes in the upper atmosphere contribute up to 90% of the total formaldehyde in the environment. Formaldehyde is an intermediate in the oxidation (or combustion) of methane, as well as of other carbon compounds, e.g. in forest fires, automobile exhaust, and tobacco smoke. When produced in the atmosphere by the action of sunlight and oxygen on atmospheric methane and other hydrocarbons, it becomes part of smog.

Formaldehyde and its adducts are ubiquitous in living organisms. It is formed in the metabolism of endogenous amino acids and is found in the bloodstream of humans and other primates at concentrations of approximately 0.1 millimolar.

Formaldehyde does not accumulate in the environment, because it is broken down within a few hours by sunlight or by bacteria present in soil or water. Humans metabolize formaldehyde quickly, converting it to formic acid, so it does not accumulate in the body.

Uses

Industrial applications

Formaldehyde is a common precursor to more complex compounds and materials. In approximate order of decreasing consumption, products generated from formaldehyde include urea formaldehyde resin, melamine resin, phenol formaldehyde resin, polyoxymethylene plastics, 1,4-butanediol, and methylene diphenyl diisocyanate. The textile industry uses formaldehyde-based resins as finishers to make fabrics crease-resistant.Formaldehyde-based materials are key to the manufacture of automobiles, and used to make components for the transmission, electrical system, engine block, door panels, axles and brake shoes.

Disinfectant and biocide

An aqueous solution of formaldehyde can be useful as a disinfectant as it kills most bacteria and fungi (including their spores). It is used to produce killed vaccines.Formaldehyde releasers are used as biocides in personal care products such as cosmetics.

Formaldehyde is also approved for use in the manufacture of animal feeds in the US. It is an antimicrobial agent used to maintain complete animal feeds or feed ingredients Salmonella negative for up to 21 days.

Tissue fixative and embalming agent

Formaldehyde preserves or fixes tissue or cells.

Drug testing

Formaldehyde and an 18 M (concentrated) sulfuric acid makes Marquis reagent—which can identify alkaloids and other compounds.

Photography

In photography, formaldehyde is used in low concentrations for process C-41 (color negative film) stabilizer in the final wash step, as well as in the process E-6 pre-bleach step, to make it unnecessary in the final wash.

Safety

The safety of formaldehyde is very complicated. It occurs naturally and is "an essential intermediate in cellular metabolism in mammals and humans." It is not acutely toxic as ingestion of many milliliters is tolerated.

The formaldehyde theory of carcinogenesis was proposed in 1978. In 1987 the U.S. EPA classified it as a probable human carcinogen, and after more studies the WHO International Agency for Research on Cancer (IARC) in 1995 also classified it as a probable human carcinogen. In the residential environment, formaldehyde exposure comes from a number of different routes; formaldehyde can off-gas from wood products, such as plywood or particle board, but it is produced by paints, varnishes, floor finishes, and cigarette smoking as well.

Removal method (home environment)
The most effective way to avoid formaldehyde is to control the source, that is, the decoration and furniture purchase from the style and materials, such as the use of wood nails or metal furniture and decoration as much as possible, reduce the glue-type woodworking products, especially to avoid cheap plywood products. At the same time, paint and wood can not be avoided when using low formaldehyde test qualified materials. Reducing the amount of formaldehyde in the house from the source is the best solution for the bottom line.

Powerful ventilation
Strong ventilation is a powerful and effective way to reduce formaldehyde concentration. It is superior to other methods, but it can only be performed if the outdoor temperature and humidity, air quality and noise are acceptable. It does not necessarily reduce the formaldehyde to a safe amount, and once the formaldehyde concentration is stopped, It will start to increase.

Activated carbon
The indoor activated carbon package can adsorb formaldehyde, and the carbon surface has many small pore structures to lock the formaldehyde molecules, but there is no other mechanism except the other. Therefore, it is ineffective after the adsorption is full, and it is necessary to change the package frequently, or even the already adsorbed formaldehyde. It was released when the temperature rose. Exposing the carbon pack to the sun outdoors can remove the gas it locks back [15] but it can only be repeated several times. The advantage is that the ultraviolet light in the drawer or in the deep room is less, and the photocatalyst fails.

Ozone device
The effective concentration of ozone is also toxic, but ozone can be decomposed in a short period of time. In the case where it is determined that there is no human or animal for a certain period of time, and the human and animal can be closed for a while before entering, the ozone generator can be turned on to reduce the amount of formaldehyde accumulation.