Antifreeze agent

An antifreeze is defined as an additive that, when added to a water-based fluid, will reduce the freezing point of the mixture [1671]. Antifreezes are used in mechanical equipment in environments below the freezing point to prevent the freezing of heat-transfer fluids. Another field of application is in cementing jobs to allow operation below the freezing point. 

Hydrate control is not included in this chapter, but is discussed in Chapter 13 because of the relative importance and difference in chemical mechanism. Many chemicals added to water will result in a depression of the freezing point. The practical application is restricted, however, because of some other unwanted effects, such as corrosion, destruction of rubber sealings in engine parts, or economic aspects. 

Freezing point depression follows the colligative laws of thermodynamics at low concentrations added to water. At the same time the boiling point generally will be increased. The freezing point depression can be readily explained from the theory of phase equilibria in thermodynamics. 

In equilibrium the chemical potential must be equal in coexisting phases. The assumption is that the solid phase must consist of one component, water, whereas the liquid phase will be a mixture of water and salt. So the chemical potential for water in the solid phase fis is the chemical potential of the pure substance. However, in the liquid phase the water is diluted with the salt. Therefore the chemical potential of the water in liquid state must be corrected. X refers to the mole fraction of the solute, that is, salt or an organic substance. The equation is valid for small amounts of salt or additives in general  

The derivative with respect to temperature will give the dependence of equilibrium concentration on temperature itself  

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Diols are applied on a multimilhon ton scale as antifreezing agents and polyester monomers (ethylene and propylene glycol) [58]. In addition, they are starting materials for various fine chemicals. Intimately coimected with the epoxidation-hydrolysis process, dihydroxylation of C=C double bonds constitutes a shorter and more atom-efficient route to 1,2-diols. Although considerable advancements in the field of biomimetic nonheme complexes have been achieved in recent years, still osmium complexes remain the most efficient and reliable catalysts for dihydroxylation of olefins (reviews [59]). 

The hydrate-formation temperamre can be reduced by the addition of antifreeze agents such as methanol, glycols [1430], or brines. The depression of the freezing point is given by... 

The classic antifreeze agents in heat-transfer liquids are brine solutions and alcohols. 

Of the commonly used antifreeze agents, brines are the most corrosive to metals of the engines and exhibit scale deposition characteristics that are... 

Dibasic salts of dicyclopentadiene dicarboxylic acid are claimed to be active as corrosion inhibitors [444], Certain salts of fatty acids (metal soaps), together with benzotriazole, are claimed to give synergistic effects for corrosion in antifreeze-agent formulations [446]. 

The choice of a corrosion inhibitor as an additive in antifreezing agents is also dependent on the mode of operation. For instance, cars are operated intermittently. Here the corrosion inhibitors must also protect the system when it is idle. Film-forming silicates can protect the system while idle. This is especially true of aluminum parts, which are introduced in cars for the sake of weight reduction. But silicones can react with ethylene glycol to form crosslinked polymers. These gels may clog lines. 

The aquatic toxicity of antifreeze agents is not strictly a function of the main component. Aquatic toxicity may come also from minor components in the formulation. Both ethylene glycol and propylene glycol are believed to be essentially nontoxic for aquatic life. 

Antifreezing agents for cement consist mainly of salts such as calcium chloride, magnesium chloride, sodium chloride, and soda. Calcium chloride is highly corrosive and very restricted in use. Some salts, especially potassium chloride, will affect the curing time of cement. The latter chemical is in fact used to increase the pot life of cement. Likewise, alcohol freezing-point depressants, such as ethylene glycol, can be also included in the composition [1022]. 

Antifreeze agents are occassionally added to reduce the freezing point of the drilling fluid itself [756,758]. Such a water-based drilling fluid is composed of water, clay or polymer, and a poly-glycerol. The drilling fluid is useful in low-temperature drilling. 

Ethanol has a lot of uses fuel, solvent, antifreeze agent, and mood-modifying substance for people. Automobiles, if suitably modified, can run on pure ethanol or, more commonly, on ethanol mixed with gasoline. In the United States gasohol is typically 10% ethanol/90% gasoline. Less conunon is E-85, which, as the name implies, is 85% ethanol. 

Pressurized water extinguishers should be hydrostatically tested to at least 200 psig (1,379 kPa). The design should provide automatic pressure release for safety upon disassembly. A listed fire extinguisher containing antifreeze agent suitable for the minimum expected temperature should be supplied when necessary. 

Table 9.5 lists the uses of ethylene oxide. Ethylene glycol is eventually used in two primary types of end products polyesters and antifreeze. About half the ethylene glycol is used for each end product. Poly(ethylene terephthalate) is the leading synthetic fiber and has other important applications in plastic film and bottles. Ethylene glycol is a common antifreezing agent especially in automobile radiators. 

Cryoprotection of crystalline samples involves either the introduction of antifreeze agents into and around the crystal (which contain 40-90% solvent)... 

Table 4.1 Antifreeze agents used in the shock cooling of macromolecular crystals...

There is one use to which levulinic acid can immediately be put. We have found that its sodium salt has ideal properties for an antifreeze agent. It has definite advantages over ethylene glycol for this purpose. It is a solid and is therefore more easily marketed than the liquid glycol. It is less corrosive to the iron parts of internal combustion engines than is tap water itself and has no detrimental effect on the rubber connections used in engines. 

XII) Ethy Alcohol Solution. Since LA is very sensitive, it was shipped and stored at KOW wet with not less than 20% (usually 25-27%) of a 50 0.5% (by wt) denatured alcohol (Ref 9, p 57). Alcohol served as an antifreezing agent. The compn of an ale soln can be detd from the table, density vs % ale after detg the density by means of a Leach pycnometer standards2ed at 25°, using the following formula ... 

Antifreeze agents are also used in fuels where severe environmental conditions are encountered. For example, a mixture of methyl alcohol, isopropyl alcohol, TM Dry-gas, and sometimes proprietary substances are used to inhibit the formation of ice from water vapor in hydrocarbon fuels. It is added directly to the gasoline. These additives are toxic and flammable. 

Aminoisoquinoline is a component of an ethylene glycol-hased corrosion inhibiting antifreeze agent. 

As to other organic substances in this context, special mention must be made of glycoproteins, which prevent blood from freezing in Arctic and Antarctic fish (De Vries, 1970 Hochachka and Somero, 1973). Glycoprotein, composed of repeated subunits of alanine and threonine bound to a disaccharide derivative of galactose, is an antifreeze agent (DeVries, 1971 Shier et al., 1972). It impedes crystal formation in blood and lowers the freezing point to -1.8°C, the lowest... 

De Vries, A.L. (1971). Glycoproteins as biological antifreeze agents in Antarctic fishes. Science, New York 172,1152-1155. 

DeVries, A.L. (1982). Biological antifreeze agents in coldwater fishes. Comp. Biochem. Physiol. 73 627-640. 

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