Petroleum solvent volatility

Odor is of prime importance because a petroleum solvent is often used in closed rooms moreover, the idea of odor is tied instinctively in the public image to toxicity. Odor is a function of the solvent s composition and volatility. Generally, the paraffin hydrocarbons are less odorous while the aromatics are more so. 

Petroleum solvents are very flammable and can cause an explosion in the presence of air. For this reason, their flash points, directiy related to volatility, are always specified. 

There are many temporary protectives on the market and it would be impracticable to describe them individually. However, they may be classified according to the type of film formed, i.e. soft film, hard film and oil film the soft film may be further sub-divided into solvent-deposited thin film, hot-dip thick film, smearing and slushing types. All these types are removable with common petroleum solvents. There are also strippable types based on plastics (deposited by hot dipping or from solvents) or rubber latex (deposited from emulsions) these do not adhere to the metal surfaces and are removed by peeling. In addition there are volatile corrosion inhibitors (V.C.I.) consisting of substances, the vapour from which inhibits corrosion of ferrous metals. 

Fractionation of petroleum by volatility, informative as it might be, does not give any indication of the physical nature of petroleum. This is more often achieved by subdivision of the petroleum into bulk fractions that are separated by a variety of solvent and adsorption methods. 

Petroleum solvents (also called naphtha) are valuable because of their good dissolving power. The wide range of naphtha available and the varying degree of volatility possible offer products suitable for many uses. 

The use of cutback asphalts has increased remarkably from 130,000 tons in 1929 (39) to about 2,390,600 tons in 1949 (126). Since these consist of paving asphalt, temporarily liquefied by means of a volatile petroleum solvent to facilitate application and manipulation in construction, control of the rate of hardening by solvent evaporation is necessary. Normally, hardening characteristics have been determined and specified by means of a distillation test, but this procedure has come to be considered inadequate. Martin (68) has suggested the evaporation index, as an improved method, and other methods are under consideration by Committee D-4 of the American Society for Testing Materials. 

Petroleum solvent-based paints contain aliphatic and aromatic hydrocarbons, ketoximes, alcohols, free monomers and plasticisers. In a general purpose petroleum solvent-based paint the volatile components are aliphatic hydrocarbons and paraffin naphtha. Odourless solvents (isoparaffinic naphtha or petroleum distillate) used in some interior oil/alkyd-based coatings can pose a danger for hypersensitive persons. 

Many useful lipid oils are extracted from a variety of plant seeds including rapeseed, soybeans, sunflowers, and com. In addition to their food uses, these oils are used in a large variety of applications including raw materials for making other chemical products, lubricants, and as biodiesel fuels. Part of the usefulness of lipid oils in many applications is due to their similarity to petroleum hydrocarbons. Volatile solvents, most commonly the 6-carbon straight-chain alkane n-hexane, CgHj4, are used to extract oils from plant sources. In this process, the solvents are distilled off from the extract and recirculated through the process. 

The health hazards of many hydrocarbon solvents are less than many other types of solvents. Proper ventilation should be provided in areas where the volatile solvents are used and skin contact with the petroleum solvents should be minimized. Inhalation of high concentrations of the hydrocarbon vapors will cause an anesthetic effect and depression of the central nervous system, and is characterized by dizziness, loss of coordination, and the feeling of being lightheaded. Removal of the individual from the exposure area and into fresh air will reverse the anesthetic... 

Light petroleum is volatile and losses of solvent occur by evaporation during measurements of optical density in spectrophotometric cells. This loss can be reduced if stoppered cells are used. Soapy emulsions are more easily broken down with light petroleum than with ether. No change of solvent is required if light petroleum can be used throughout the analytical process. 

Vapor pressure is also used as an indirect measure of the evaporation rate of volatile petroleum solvents. 

Emulsives are solutions of toxicant in water-immiscible organic solvents, commonly at 15 ndash 50%, with a few percent of surface-active agent to promote emulsification, wetting, and spreading. The choice of solvent is predicated upon solvency, safety to plants and animals, volatility, flammabiUty, compatibihty, odor, and cost. The most commonly used solvents are kerosene, xylenes and related petroleum fractions, methyl isobutyl ketone, and amyl acetate. Water emulsion sprays from such emulsive concentrates are widely used in plant protection and for household insect control. 

In the wood rosin process, rosin is isolated from aged pine stumps that have been left in fields cleared for farming or lumbering operations. The stumps are cut and shredded to pieces the size of matchsticks. The wood chips are then extracted with an appropriate solvent, eg, aUphatic or aromatic petroleum hydrocarbons or ketones. The extract is fractionally separated into nonvolatile cmde rosin, volatile extractibles, and recovered solvent. The dark rosin is usually refined further to lighter-colored products using selective solvents or absorption. 

Acids that are solids can be purified in this way, except that distillation is replaced by repeated crystallisation (preferable from at least two different solvents such as water, alcohol or aqueous alcohol, toluene, toluene/petroleum ether or acetic acid.) Water-insoluble acids can be partially purified by dissolution in N sodium hydroxide solution and precipitation with dilute mineral acid. If the acid is required to be free from sodium ions, then it is better to dissolve the acid in hot N ammonia, heat to ca 80°, adding slightly more than an equal volume of N formic acid and allowing to cool slowly for crystallisation. Any ammonia, formic acid or ammonium formate that adhere to the acid are removed when the acid is dried in a vacuum — they are volatile. The separation and purification of naturally occurring fatty acids, based on distillation, salt solubility and low temperature crystallisation, are described by K.S.Markley (Ed.), Fatty Acids, 2nd Edn, part 3, Chap. 20, Interscience, New York, 1964. 

On-line SFE-GC finds use especially in petroleum-related applications [54], but has also been applied to polymer additives [47,55]. PBT polymers were extracted at 200 bar and 55 °C for the determination of carbonic acid diphenyl esters and other volatiles, using on-line SFE-GC-MS [47]. Extraction of entrained volatiles is a quality test for some polymers. SFE-GC-FTIR-MS has been employed to reveal the cause of odour of a smelly hose (a plasticiser) [56]. SFE-GC can also profitably be used for the determination of residual solvents in polymers such as benzene, toluene and o-xylene [57]. Oligomers of PE (up to 1000 Da) were determined by GC after supercritical fluid extraction [58]. 

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