Antifreeze solutions, aqueous

TABLE 5.13 Compositions of Aqueous Antifreeze Solutions Continued)... 

Antifreeze solutions are aqueous solutions of ethylene glycol, C2H602 (d = 1.12 g/mL). In Connecticut, cars are winterized by filling radiators with an antifreeze solution that will protect the engine for temperatures as low as — 20°F. 

An aqueous antifreeze solution is 40.0% ethylene glycol (CjTUOi) by mass. The density of the solution is 1.05 g/cm3. Calculate the molality, molarity, and mole fraction of the ethylene glycol. 

Propylene glycol, C3H5(OH)2, is sometimes used in automobile antifreeze solutions. If an aqueous solution has a mole fraction XcjH5(OH)2 0.100, calculate (a) the percent propylene glycol by mass (b) the molality of the propylene glycol in the solution. 

Miscellaneous Derivatives. Fimehc acid is used as an intermediate in some pharmaceuticals and in aroma chemicals ethylene brassylate is a synthetic musk (114). Salts of the diacids have shown utUity as surfactants and as corrosion inhibitors. The alkaline, ammonium, or organoamine salts of glutaric acid (115) or C-5—C-16 diacids (116) are useflil as noncorrosive components for antifreeze formulations, as are methylene azelaic acid and its alkah metal salt (117). Salts derived from C-21 diacids are used primarily as surfactants and find apphcation in detergents, fabric softeners, metal working fluids, and lubricants (118). The salts of the unsaturated C-20 diacid also exhibit anticorrosion properties, and the sodium salts of the branched C-20 diacids have the abUity to complex heavy metals from dilute aqueous solutions (88). 

Aqueous solutions of many salts, of the common strong acids (hydrochloric, nitric and sulphuric), and of bases such as sodium hydroxide and potassium hydroxide are good conductors of electricity, whereas pure water shows only a very poor conducting capability. The above solutes are therefore termed electrolytes. On the other hand, certain solutes, for example ethane-1,2-diol (ethylene glycol) which is used as antifreeze , produce solutions which show a conducting capability only little different from that of water such solutes are referred to as non-electrolytes. Most reactions of analytical importance occurring in aqueous solution involve electrolytes, and it is necessary to consider the nature of such solutions. 

The improvements have come by way of petroleum oils with viscosity index improvers, or synthetics with naturally high viscosity index. The problem of packing deterioration, or rusting, is chiefly a chemical matter. Hydraulic fluids for the various applications include those made from petroleum, synthetic oils, and aqueous solutions containing antifreeze and rust inhibitors. Antifoam agents are necessary in some hydraulic fluids. 

Aqueous solutions of propylene glycol display excellent antifreeze properties and are therefore valuable as low temperature heat-transfer fluids. For applications involving indirect food contact, heat-transfer fluids formulated with the USP grade product are preferred, since there could be inadvertent contact with a food product. These fluids are commonly used in the brewing and dairy industries as well as in refrigerated display cases in retail grocery stores. 

Salt Brines Salt brines are water solutions of inorganic salts. Aqueous CaCl2 solutions of maximum 25% are recommended down to -20 °C. Salt brines are low cost but expensive in operation. Antifreezes described below are preferable. 

Furthermore, life should be considered possible in aqueous environments that are extreme in their solute content, in their acidity or alkalinity, and in their temperature range, especially with ammonia as an antifreeze in low-temperature water-ammonia eutectics. The committee sees no reason to exclude the possibility of life in environments as diverse as the aerosols above Venus and the water-ammonia eutectics of Titan. It seems that life is less likely in more exotic solvents—such as liquid dinitrogen, liquid methane, and supercritical dihydrogen—but this conclusion is based on few data. 

---