Contact with water

When water comes into contact with hot water, the water undergoes a very sudden expansion causing a foaming affect. This foaming effect is dangerous to the personnel and could cause fire and explosion. For this reason, care must always be taken when handling bitumen emulsion followed by bitumen. 

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In addition to their antiknock properties, organic lead compounds possess bactericidal properties and motor fuels with lead are known to inhibit bacterial growth during storage in contact with water. With the disappearance of lead-based compounds, it is necessary to incorporate biocides from the cyclic imine family, (piperidine, pyrrolidine, hexamethyleneimine), alkylpropylene diamines or imidazolines (Figure 9.2). 

CAUTION. Sodium must be handled with great care and under no circumstances may the metal be allowed to come into contact with water as a dangerous explosion may result. Sodium is stored under solvent naphtha or xylene it should not be handled with the fingers but with tongs or pincers. Waste or scrap pieces of sodium should be placed in a bottle provided for the purpose and containing solvent naphtha or xylene they should never be thrown into the sink or into the waste box. If it is desired to destroy the scrap sodium, it should be added in small portions to rather a large quantity of methylated spirit. 

Sodium metal should be handled with great care. It cannot be maintained in an inert atmosphere and contact with water and other substances with which sodium reacts should be avoided. 

FIGURE 19 6 Space filling model of a micelle formed by association of car boxylate ions derived from a long chain carboxylic acid The hydrocarbon chains tend to be on the inside and the carboxylate ions on the surface where they are in contact with water mole cules and metal cations... 

The structure of cholic acid helps us understand how bile salts such as sodium tauro cholate promote the transport of lipids through a water rich environment The bot tom face of the molecule bears all of the polar groups and the top face is exclusively hydrocarbon like Bile salts emulsify fats by forming micelles m which the fats are on the inside and the bile salts are on the outside The hydrophobic face of the bile salt associates with the fat that is inside the micelle the hydrophilic face is m contact with water on the outside... 

In addition to hydrogen bonding between the two polynucleotide chains the double helical arrangement is stabilized by having its negatively charged phosphate groups on the outside where they are m contact with water and various cations Na" Mg and ammonium ions for example Attractive van der Waals forces between the... 

Molybdenum hexafluoride [7783-77-9] MoF, is a volatile liquid at room temperature. It is very moisture sensitive, hydrolysing immediately upon contact with water to produce HF and molybdenum oxyfluorides. MoF should therefore be handled in a closed system or in a vacuum line located in a chemical hood. The crystals possess a body-centered cubic stmcture that changes to orthorhombic below —96° C (1,2). The known physical properties are Hsted in Table 1. 

Properties. Silver difluoride melts at 690°C, bods at 700°C, and has a specific gravity of 4.57. It decomposes in contact with water. Silver difluoride may react violently with organic compounds, quite often after an initial induction period. Provisions must be made to dissipate the heat of the reaction. Small-scale experiments must be mn prior to attempting large-scale reactions. 

All the simple peroxides form hydrogen peroxide (qv) on contact with water. Some, eg, sodium peroxide, hydrolyze almost instantaneously ... 

The purified acid is recovered from the loaded organic stream by contacting with water in another countercurrent extraction step. In place of water, an aqueous alkafl can be used to recover a purified phosphate salt solution. A small portion of the purified acid is typically used in a backwashing operation to contact the loaded organic phase and to improve the purity of the extract phase prior to recovery of the purified acid. Depending on the miscibility of the solvent with the acid, the purified acid and the raffinate may be stripped of residual solvent which is recycled to the extraction loop. The purified acid can be treated for removal of residual organic impurities, stripped of fluoride to low (10 ppm) levels, and concentrated to the desired P2 s Many variations of this basic scheme have been developed to improve the extraction of phosphate and rejection of impurities to the raffinate stream, and numerous patents have been granted on solvent extraction processes. 

Lubricious Coatings for Biomaterials. Coatings of poly(ethylene oxide) when dry are tactile. If brought into contact with water, the poly(ethylene oxide) hydates rapidly and forms a lubricious coating. This type of technology is of great interest for biomedical devices introduced into the human body, such as catheters and endotracheal tubes, and for sutures (114—117). 

Contact with elemental selenium does not injure the skin. Selenium dioxide, however, upon contact with water, sweat, or tears, forms selenous acid, a severe skin irritant. Selenium oxyhaHdes are extremely vesicant and cause bums when in contact with human skin (91,92). Hydrogen selenide affects the mucous membranes of the upper respiratory tract and the eyes (93). 

In general, the sulfolane extraction unit consists of four basic parts extractor, extractive stripper, extract recovery column, and water—wash tower. The hydrocarbon feed is first contacted with sulfolane in the extractor, where the aromatics and some light nonaromatics dissolve in the sulfolane. The rich solvent then passes to the extractive stripper where the light nonaromatics are stripped. The bottom stream, which consists of sulfolane and aromatic components, and which at this point is essentiaHy free of nonaromatics, enters the recovery column where the aromatics are removed. The sulfolane is returned to the extractor. The non aromatic raffinate obtained initially from the extractor is contacted with water in the wash tower to remove dissolved sulfolane, which is subsequently recovered in the extract recovery column. Benzene and toluene recoveries in the process are routinely greater than 99%, and xylene recoveries exceed 95%. 

Tellurium Nitride. TeUurium nitride [12164-01 -0] Te N is an unstable, citron-yeUow soHd that detonates easUy when heated or stmck, but it can be kept under dry chloroform. It is said to explode on contact with water, possibly because of the heat of wetting. 

Enhanced Oil Recovery. A hydrocarbon solution of TYZOR TPT, TYZOR TBT, or TYZOR TOT can be pumped into the porous zones of an oil-bearing formation upon contact with water, an amorphous, gelatinous plug is formed, which allows water to be diverted to less porous... 

Hydrophobic substances are soluble in nonpolar solvents, whereas their solubiUty in water is very limited. Many of these substances are also soluble in fats and Hpids and are also called hpophile compounds. Such substances have a tendency to avoid contact with water and to associate with a nonpolar, nonaqueous environment, such as a surface, eg, an organic particle, a particle containing organic material, or the lipid-containing biomass of an organism. 

Scale. Scale deposits are formed by precipitation and crystal growth at a surface in contact with water. Precipitation occurs when solubiUties are exceeded either in the bulk water or at the surface. The most common scale-forming salts that deposit on heat transfer surfaces are those that exhibit retrograde solubiUty with temperature. 

The barium crowns are usually broken into smaller pieces and can be sold in this form or cast or extmded into bars or wire. Usually the metal is packaged in argon-fiked plastic bags inside argon-fiked steel containers. Barium is classed as a flammable soHd and cannot be mailed. It should be stored in a wek-ventilated area so as to remove any hydrogen formed through reaction with water vapor. It should not be stored where contact with water is possible. 

Barium also presents a hydrogen explosion ha2ard if allowed to come iato contact with water or atmospheric moisture, and must always be kept dry and preferably sealed ia the shipping containers. 

Anode Corrosion Reaction. Ziac might at first appear to be an unusual choice for battery anode material, because the metal is thermodynamically unstable ia contact with water... 

Procedures for shipping boric acid esters depend on the particular compound. Aryl borates produce phenols when in contact with water and are therefore subject to shipping regulations governing such materials and must carry a Corrosive Chemical label. Lower alkyl borates are flammable, flash points of methyl, ethyl, and butyl borates are 0, 32, and 94°C, respectively, and must be stored in approved areas. Other compounds are not hazardous, and may be shipped or stored in any convenient manner. Because borate esters are susceptible to hydrolysis, the more sensitive compounds should be stored and transferred in an inert atmosphere, such as nitrogen. 

Sobd sodium borobydride does not ignite upon contact with moisture and is not shock sensitive. These characteristics allow it to be handled safely in ab. Because it does Hberate hydrogen upon contact with water it should be handled with care. 

Calcium metal and most calcium compounds are nontoxic. In massive pieces the metal does not spontaneously bum in air. Calcium can be touched with dry bare hands without harm. Care must be taken, however, to avoid contact with water owing to the exothermic Hberation of hydrogen and the resulting explosion hazard. Calcium must always be kept dry and preferably sealed in the shipping containers. 

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