Preservatives for biological specimens

Formaldehyde (bp = — 21°C) is ordinarily found in the laboratory in the form of a concentrated water solution (37% HCHO) known as formalin. At one time it was widely used as a preservative for biological specimens. That application has declined now that formaldehyde has been shown to be carcinogenic. Industrially, it is still used as a component of adhesives used in making plywood and fiberboard. 

The systematic names of a/dehydes end in -al the systematic names of keto cs end in -one. The simplest ketone, propanone, known familiarly as acetone, has three carbon atoms. Because of its solvent properties, acetone is used in nail polish remover. The simplest aldehyde, methanal, also known as formaldehyde, is perhaps most familiar because it was formerly routinely used as a preservative for biological specimens. 

Because it is a starting material for the synthesis of many resins and plastics, billions of pounds of formaldehyde are produced annually in the United States by the oxidation of methanol (CH3OH). Formaldehyde is also sold as a 37% aqueous solution called formalin, which has been used as a disinfectant, antiseptic, and preservative for biological specimens. Formaldehyde, a product of the incomplete combustion of coal and other fossil fuels, is partly responsible for the irritation caused by smoggy air. 

Use Antibiotic (used as a preservative for biological specimens) embalming fluids. 

Formalin is an aqueous solution of formaldehyde, HCHO, used as a preservative for biological specimens. How many grams of formaldehyde must be used to prepare 2.5 L of 12.3 M formalin ... 

HCOH) A colorless gaseous aldehyde. It is manufactured by the oxidation of methanol (500°C and a silver catalyst) 2CH3OH + 02 2HCOH + 2H2O The compound is used in the manufacture of urea-formaldehyde resins. A solution of methanal (40%) in water is called formalin. It is extensively used as a preservative for biological specimens. 

Picric acid, 2,4,6-trinitrophenol, is used in many laboratories, especially for staining in microscopy in biological laboratories. It is sometimes used in organic laboratories for preparing crystalline picrate salts. It has also been used for creatinine measurements in clinical and drug screening, and as a preservative for biological specimens. 

Formaldehyde has been widely used as a preservative for biological specimens, although that use has been largely discontinued because it is a suspected carcinogen. It is, however, used in embalming fluids. 

In bulk polymerization, no solvents are employed and the monomer acts as the solvent and continuous phase in which the process is carried out. Commercial bulk processes for acrylic polymers are used mainly m the production of sheets, rods and tubes. Rulk processes are also used on a much smaller scale in the preparation of dentures and novelty items and in the preservation of biological specimens. Acrylic castings are produced by pouring monomers or partially polymerized sirups into suitably designed molds and completing the polymerization. Acrylic bulk... 

Synonyms and trade names picronitric acid, 2,4,6-trinitrophenol, trinitrophenol Use and exposure Picric acid is a white to yellowish crystalline substance and highly flammable. It is used in the manufacture of fireworks, matches, electric batteries, colored glass, explosives, and disinfectants. Pharmaceutical, textile, and leather industries also make use of picric acid. Bouin s picro-formol is used as a preservative solution for biological specimens in laboratories. Toxicity and health effects Picric acid causes different adverse effects on the skins of animals and humans, like allergies, dermatitis, irritation, and sensitization. Absorption of picric acid by the system causes headache, fever, nausea, diarrhea, and coma. In high concentrations, picric acid is known to... 

Formaldehyde has long been used as a disinfectant and as a preservative (including embalming fluid) for biological specimens. Its main use is in the production of certain plastics and in binders for plywood. Many important natural substances are aldehydes and ketones. Examples include sex hormones, some vitamins, camphor, and the flavorings extracted from almonds and cinnamon. Aldehydes contain a carbon-oxygen double bond, so they are very reactive compounds. As a result, they are valuable in organic s)mthesis, particularly in the construction of carbon chains. 

Formaldehyde, CH2O, has many uses, including the preservation of biological specimens. Draw a reasonable Lewis structure for formaldehyde. 

Hydrochloric and nitric acids have been used as preservatives for urine specimens for metal analyses, and mineral acids are extensively used in graphite furnace analysis of trace elements in biological specimens (e.g. Gills et al., 1974 Stoeppler and Brandt, 1980). Historically, concentrations of trace elements in commercially available acids have been incompatible with analysis of trace elements in biological samples (Kuehner et al., 1972). However, present commercial ultra pure hydrochloric, nitric, sulphuric and perchloric acids have been reported to be suitable for trace element analysis in urine without further purification (Golimowski et al., 1979 Brown et al., 1981 Veillon et al., 1982). 

Formaldehyde, HCHO, is an economically important aldehyde. It s used as a solvent and for preservation of biological specimens. Formaldehyde is also used in the synthesis of certain polymers, such as Bakelite and Melmac (used in melamine dishes). Other aldehydes, especially those with a benzene ring in their structure, have pleasing odors and, like esters, are used in the perfume and flavoring industry. 

Formaldehyde is a liquid with an acrid smell. Its toxicity to bacteria makes it useful as a preservative of biological specimens. Formaldehyde is also present in wood smoke and aids in the preservation of smoked meats. Formaldehyde s presence in smoke is partially responsible for the burning and tearing of eyes that occur around a campfire. 

Lower aldehydes are generally water soluble although they cannot act as hydrogen-bond donors, they are excellent hydrogen-bond acceptors. The solution of formaldehyde in water is referred to as formalin and is widely used for the preservation of biological specimens. 

Write the complete Lewis structure for each of the following compounds (a) formaldehyde, HCHO, which as its aqueous solution formalin is used to preserve biological specimens (b) methanol, CH3OH, the toxic compound also called wood alcohol (c) glycine, H2C(NH2)COOH, the simplest of the amino acids, the building blocks of proteins. 

Bacallao, R., Morgane, B., Stelzer, E. H. K., and DeMey, J. (1989) Guiding principles of specimen preservation for confocal fluorescence microscopy, in Handbook of Biological Confocal Microscopy (Pawley, J. B., ed.). Plenum, New York, pp. 197-205. 

The IUPAC rules for naming aldehydes append the suffix -al to the parent name. The aldehyde carbon is always the first carbon in the chain, so a locant is not necessary. The simplest aldehyde, methanal, is commonly known as formaldehyde, a highly toxic gas used to preserve biological specimens. Ethanal is the next aldehyde, although most organic chemists call it acetaldehyde. 2,2,2-Tri-chloroethanal, more commonly known as chloral, reacts with water to form the sedative chloral hydrate. Phenylmethanal, more commonly known as benzalde-hyde, is used as artificial cherry or almond flavoring. Nomenclature examples of aldehydes are shown in Figure 11.34. 

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