Methanol, properties toxicity

One very important property of methanol needs to be mentioned methanol is toxic. (Actually, all alcohols are toxic. Ethanol, used in alcohoUc beverages, is merely the least toxic alcohol.) Methanol attacks the optic nerves and drinking it can lead to blindness. 

Methanol, l-isoquinolyl(phenyl)-confonnation, 2, 110 Methanol, pyrimidinyl-synthesis, 3, 113 Methanol, tetrahydropyran-2-yl-microwave spectra, 3, 625 Methantheline as neurotransmitter, 1, 175 therapeutic properties, 3, 882 Methaphenilene biological activity, 4, 911 Methapyrilene biological activity, 4, 911 toxicity, 4, 912 Methaqualone, 3, 150 as anticonvulsant, 1, 166 pyrido[2,3-d]pyrimidine analogues metabolism, 3, 205 as sedative, 1, 166 Metharbitone as anticonvulsant, 1, 166 Methazolamide... 

The first use of supercritical fluid extraction (SFE) as an extraction technique was reported by Zosel [379]. Since then there have been many reports on the use of SFE to extract PCBs, phenols, PAHs, and other organic compounds from particulate matter, soils and sediments [362, 363, 380-389]. The attraction of SFE as an extraction technique is directly related to the unique properties of the supercritical fluid [390]. Supercritical fluids, which have been used, have low viscosities, high diffusion coefficients, and low flammabilities, which are all clearly superior to the organic solvents normally used. Carbon dioxide (C02, [362,363]) is the most common supercritical fluid used for SFE, since it is inexpensive and has a low critical temperature (31.3 °C) and pressure (72.2 bar). Other less commonly used fluids include nitrous oxide (N20), ammonia, fluoro-form, methane, pentane, methanol, ethanol, sulfur hexafluoride (SF6), and dichlorofluoromethane [362, 363, 391]. Most of these fluids are clearly less attractive as solvents in terms of toxicity or as environmentally benign chemicals. Commercial SFE systems are available, but some workers have also made inexpensive modular systems [390]. 

DMC is classified as a flammable liquid, smells like methanol, and does not have irritating or mutagenic effects, either by contact or inhalation. Therefore, it can be handled safely without the special precautions required for the poisonous and mutagenic methyl halides and DMS, and extremely toxic phosgene. Some physicochemical properties of DMC are listed in Table 4.2. 

Properties and handling. Methanol is a colorless, volatile liquid at room temperature with an alcoholic smell. It mixes with water in all proportions and burns with a pale blue flame. Methanol is highly toxic. As little as a fifth of a shot (lOcc) can cause blindness. Larger amounts kill. It should never be applied to the body as a rubbing alcohol because the vapors are so toxic. 

There remains little more for the operator to decide. Sometimes, alternative but similar solvent mixtures that have a lower viscosity or higher solute diffusivity could be selected. For example, a n-hexane/methanol mixture might be chosen as an alternative to the more viscous n-heptane/isopropyl alcohol mixture as it has similar elution properties. However, it will be shown later, that if a fully optimized column is employed the viscosity of the mobile phase does not seem to effect the column performance as it is taken into account in the optimization procedure. The operator would, under some circumstances, be free to choose less toxic or less costly solvents for example, in reverse phase chromatography the operator could select methanol/ water solvent mixtures as opposed to acetonitrile/water mixture on the basis of lower cost or less... 

Since nonpolar lipids (e.g., triacylglycerols) are generally not readily soluble in methanol, a solvent that can dissolve both neutral and polar lipids is necessary to facilitate the reaction in methanol. Toluene is chosen for this purpose because of its good solvent properties and relatively low toxicity. 

The powdered plant material maximizes polyphenolic extraction because of its high contact area with solvent and easy destruction of biological cell walls. Ethanol may be employed instead of methanol in routine extractions to avoid the toxic properties of methanol. The main advantage of methanol over ethanol is its lower boiling point. 

A serious problem results from the fact that methanol is a toxic fluid (extreme permissible concentration of methanol in the air is 5 mg/m3) and handle it is possible only in specialised laboratories. For the pipeline laboratory research it is useful to find such substitute of methanol, which is absolutely harmless and its physical properties (density and viscosity) strictly correspond to methanol. 

Methanol has similar physical properties to ethanol, but it is toxic and ethanol is therefore the preferred solvent in most applications, e.g. medicinal agents. However, in synthetic procedures methanol is more commonly used because of its greater volatility and ease of removal under vacuum. 

The toxic properties of methanol are the result of accumulation of the formate intermediate in the blood and tissues of exposed individuals. Formate accumulation produces metabolic acidosis leading to the characteristic ocular toxicity (blindness) observed in human methanol poisonings. 

Properties Dark-brown solid. Setting point 62.5C. Soluble in acetone, methanol, and xylene. Hazard Toxic by ingestion. 

Properties Buff to light-brown flakes. Bulk d 26-29 lb/cu ft, pH of water-saturated solution 9.0-13.0. Soluble in water methanol and acetone. Hazard Toxic by ingestion. 

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