Aqueous solutions temperature effects

A combination of aluminum chlorohydrate and a polyamine, such as poly (diallyldimethyl ammonium chloride), in aqueous solution is effective at elevated temperatures for an oil-in-water emulsion [787]. 

The peroxygen bleaches, typically perborate or percarbonate salts, produce peroxide in aqueous solutions. The effectiveness of peroxide as an oxidizing agent at relatively low wash temperatures (120 to 140°F) is unfortunately minimal. Peracids (RC(O)OOH), which can be generated by the activation of carboxylic acids by peroxide or can be added directly, have not found use in LADD compositions in spite of their relatively high oxidation potentials because of their instability in aqueous solution. 

Frozen Aqueous Solutions Concentration Effects. As solute is rejected by the growing ice and as its concentration increases in the shrinking liquid phase, the temperature drops toward the eutectic point, where the entire system approaches complete solidification. Of major importance is the fact that a highly concentrated liquid phase can persist indefinitely at any point above the eutectic temperature. 

These compounds are always formed when carbon comes into contact with air or Og at room temperature. Their formation can only be avoided when contact is prevented. These basic compounds may coexist on the surface of the carbon with the acid-forming O compounds. With highly adsorptive carbon these compounds may exert, in aqueous solution, an effect equivalent to a concentration of 100 meq. of OH" ions per 100 g. of carbon. 

Micellar solutions are sometimes called ordered media [12]. The chemical order in a micellar solution seems to be greater than in a classical solution. Equation 2.9 shows ftiat the micellization of surfactant molecules obeys the second principle of thermodynamics. It seems that the surfectant hydrocarbon chains have a much higher freedom of motion inside the micelle core than in the water bulk [13]. The micelle structure minimizes the molecule energy. The large entropy increai of water molecules associated with the removal of nonpolar surfactant tails from the aqueous solution (hydrophobic effect) is the main micelle driving force. Electrostatic forces tend to separate the polar heads that bear the same charge. The whole micelle is an equilibrium between these forces. This equilibrium is very sensitive to any chemical additive or parameter that can act on any of the forces, such as salts, polar or nonpolar solutes, temperature and/or pressure. 

The proton transfer reactions of bis(dimethylglyoximato)cobalt(III) complexes [Co(III)(dmgH)2X2]" (X = NH3 or CN) with OH have been studied in dioxane-water media by temperature jump techniques. The rate constant, kf, for the direct proton transfer from [Co(III)(dmgH)2X2]" to OH was found to be 1.6 x 10 -2.9 x 10 A/ s in aqueous solution. The effect of the dioxane constant has been studied in detail. 

SODIUTH CARBONATE. NajCOj. Solid sodium carbonate was very corrosive to alloy 3003 in laboratory tests conducted under conditions of 100% relative humidity at ambient temperature. In other laboratory tests, aqueous solutions of sodium carbonate (1% to 10%)) w ere vety corrosive to 1100 alloy at ambient temperature. In the same tests, the action of these aqueous solutions was effectively inhibited by the addition of silicates. Aluminum alloy hopper cars have been used to transport sodium carbonate. See also Ref (Dp. 142, (2) p. 660, (3) pp. 23, 67, (4) pp. 34, 37, 50, 76, 86, 96, 103. 

Alkali treatment of natural fibers, also referred to as mercerization, is an old and most widely used method for modifying ceUulose-based natural fibers [30-36]. The most favorable alkali solution for mercerization is sodium hydroxide (NaOH) aqueous solution. The effect of alkali treatment on the properties of the composite as well as on the natural fibers strongly depends on alkali solution type, alkali concentration, treatment time, treatment temperature, and treatment tool. Alkali treatment may cause fibrillation of pristine natural fibers, resulting in the breakdown of individual fibers with smaller fiber diameter. This phenomenon can not only increase the aspect ratio of reinforcing natural fibers but also roughen the fiber surfaces. As a result, the fiber-matrix interfacial adhesion may be enhanced and the... 

Assume that an aqueous solute adsorbs at the mercury-water interface according to the Langmuir equation x/xm = bc/( + be), where Xm is the maximum possible amount and x/x = 0.5 at C = 0.3Af. Neglecting activity coefficient effects, estimate the value of the mercury-solution interfacial tension when C is Q.IM. The limiting molecular area of the solute is 20 A per molecule. The temperature is 25°C. 

To obtain a maximum yield of the acid it is necessary to hydrolyse the by-product, iaoamyl iaovalerate this is most economically effected with methyl alcoholic sodium hydroxide. Place a mixture of 20 g. of sodium hydroxide pellets, 25 ml. of water and 225 ml. of methyl alcohol in a 500 ml. round-bottomed flask fitted with a reflux (double surface) condenser, warm until the sodium hydroxide dissolves, add the ester layer and reflux the mixture for a period of 15 minutes. Rearrange the flask for distillation (Fig. II, 13, 3) and distil off the methyl alcohol until the residue becomes pasty. Then add about 200 ml. of water and continue the distfllation until the temperature reaches 98-100°. Pour the residue in the flask, consisting of an aqueous solution of sodium iaovalerate, into a 600 ml. beaker and add sufficient water to dissolve any solid which separates. Add slowly, with stirring, a solution of 15 ml. of concentrated sulphuric acid in 50 ml. of water, and extract the hberated acid with 25 ml. of carbon tetrachloride. Combine this extract with extract (A), dry with a httle anhydrous magnesium or calcium sulphate, and distil off the carbon tetrachloride (Fig. II, 13, 4 150 ml. distiUing or Claisen flask), and then distil the residue. Collect the wovaleric acid 172-176°. The yield is 56 g. 

The rat LD qS are 13, 3.6 (oral) and 21, 6.8 (dermal) mg/kg. Parathion is resistant to aqueous hydrolysis, but is hydroly2ed by alkah to form the noninsecticidal diethjlphosphorothioic acid and -nitrophenol. The time required for 50% hydrolysis is 120 d ia a saturated aqueous solution, or 8 h ia a solution of lime water. At temperatures above 130°C, parathion slowly isomerizes to 0,%diethyl 0-(4-nitrophenyl) phosphorothioate [597-88-6] which is much less stable and less effective as an insecticide. Parathion is readily reduced, eg, by bacillus subtilis ia polluted water and ia the mammalian mmen to nontoxic 0,0-diethyl 0-(4-aminophenyl) phosphorothioate, and is oxidized with difficulty to the highly toxic paraoxon [511-45-5] diethyl 4-nitrophenyl phosphate d 1.268, soluble ia water to 2.4 mg/L), rat oral LD q 1.2 mg/kg. 

Concentration and Molecular Weight Effects. The viscosity of aqueous solutions of poly(ethylene oxide) depends on the concentration of the polymer solute, the molecular weight, the solution temperature, concentration of dissolved inorganic salts, and the shear rate. Viscosity increases with concentration and this dependence becomes more pronounced with increasing molecular weight. This combined effect is shown in Figure 3, in which solution viscosity is presented as a function of concentration for various molecular weight polymers. 

The viscosity of the aqueous solution is also significantly affected by temperature. In polymers of molecular weights (1-50) x 10 , the solution viscosity may decrease by one order of magnitude as the temperature of measurement is increased from 10 to 90°C. Figure 5 shows this effect. 

Micellar properties are affected by changes in the environment, eg, temperature, solvents, electrolytes, and solubilized components. These changes include compHcated phase changes, viscosity effects, gel formation, and Hquefication of Hquid crystals. Of the simpler changes, high concentrations of water-soluble alcohols in aqueous solution often dissolve micelles and in nonaqueous solvents addition of water frequendy causes a sharp increase in micellar size. 

The effective surface viscosity is best found by experiment with the system in question, followed by back calculation through Eq. (22-55). From the precursors to Eq. (22-55), such experiments have yielded values of [L, on the order of (dyn-s)/cm for common surfactants in water at room temperature, which agrees with independent measurements [Lemhch, Chem. Eng. ScL, 23, 932 (1968) and Shih and Lem-lich. Am. Inst. Chem. Eng. J., 13, 751 (1967)]. However, the expected high [L, for aqueous solutions of such sldn-forming substances as saponin and albumin was not attained, perhaps because of their non-newtonian surface behavior [Shih and Lemhch, Ind. Eng. Chem. Fun-dam., 10, 254 (1971) andjashnani and Lemlich, y. Colloid Inteiface ScL, 46, 13(1974)]. 

The vapor pressure is reduced. This has a significant effect on the rate of release of material boiling at less than ambient temperature. It may be possible to store an aqueous solution at atmospheric pressure, such as aqueous ammonium hydroxide instead of anhydrous ammonia. 

In this study we examined the influence of concentration conditions, acidity of solutions, and electrolytes inclusions on the liophilic properties of the surfactant-rich phases of polyethoxylated alkylphenols OP-7 and OP-10 at the cloud point temperature. The liophilic properties of micellar phases formed under different conditions were determined by the estimation of effective hydration values and solvatation free energy of methylene and carboxyl groups at cloud-point extraction of aliphatic acids. It was demonstrated that micellar phases formed from the low concentrated aqueous solutions of the surfactant have more hydrophobic properties than the phases resulting from highly concentrated solutions. The influence of media acidity on the liophilic properties of the surfactant phases was also exposed. 

R. Zana, C. Weill. Effect of temperature on the aggregation behavior of nonionic surfactants in aqueous solutions. J Physique Lett 46 L953-L960, 1985. 

Anhydrous NaC102 crystallizes from aqueous solutions above 37.4° but below this temperature the trihydrate is obtained. The commercial product contains about 80% NaC102. The anhydrous salt forms colourless deliquescent crystals which decompose when heated to 175-200° the reaction is predominantly a disproportionation to C103 and Cl but about 5% of molecular O2 is also released (based on the C102 consumed). Neutral and alkaline aqueous solutions of NaC102 are stable at room temperature (despite their thermodynamic instability towards disproportionation as evidenced by the reduction potentials on p. 854). This is a kinetic activation-energy effect and, when the solutions are heated near to boiling, slow disproportionation occurs ... 

---