Salicylic Acid In Water Research Articles

Experimental data of solubility at different temperatures: a simple technique

This article describes a simple and inex- pensive experimental technique, easy to set-up in a laboratory, for the measurement of solute solubilities in liquids (or gases). Experimental values of solubility were determined for the dissolution of benzoic acid in water, at 293-338 K, of 2-naphthol in water, at 293-373 K, and of salicylic acid in water, at 293-343 K. The experimental results obtained are in good agree- ment with the theoretical values of solubilities presented in literature. Empirical correlations are presented for the prediction of solubility over the en- tire range of temperatures studied, and they are shown to give the solubility value with very good accuracy. List of symbols a radius of the active sphere (m) A area of a soluble sphere (m 2 ) c solute concentration (kg/m 3 ) c0 bulk concentration of solute (kg/m 3 ) c * saturation concentration of solute (kg/m 3 ) cout concentration in the outlet stream (kg/m 3 ) d diameter of inert particles (m) d1 diameter of active sphere (m) D diameter of test column (m) DL longitudinal dispersion coefficient (m 2 /s) D¢m effective molecular diffusion coefficient (m 2 /s) DT transverse (radial) dispersion coefficient (m 2 /s) K permeability in Darcy's law (m 3 s/kg) k average mass transfer coefficient (m/s) L length of test column (m) n number of soluble spheres (-) p pressure (kg/ms 2 ) Pe¢ peclet number based on diameter of active

Structure and Stability of Salicylic Acid−Water Complexes and the Effect of Molecular Hydration on the Spectral Properties of Salicylic Acid

Density functional theory with B3LYP parametrization and 6-311++G(d,p) basis set has been used to investigate the structure and stability of salicylic acid-water complexes. The vertical excitation energies for these complexes have been computed using time-dependent density functional theory (with B3LYP parametrization and a 6-311++G(d,p) basis set). It is shown that the hydrogen bond between the carboxylic hydrogen and the oxygen of water is the strongest among all possible hydrogen bonds in the system. The hydrogen bond strength in salicylic acid-water complexes seems to be nearly additive. The change in absorption maximum (lambda(max)) corresponding to the vertical excitation energy for the first three excited singlet and triplet states of the complex with 1-3 water molecules is nominal (approximately 1-3 nm). But with the addition of the fourth water molecule, the lambda(max) for S(1) and T(1) decreases by approximately 17 nm and it increases for S(2) and S(3) by about the same amount. The decrease in lambda(max) for transition to the T(2) state on the addition of the fourth water molecule is only approximately 9 nm. There seems to be an intersystem crossing between the S(1) and T(3) states that could account for the observed fluorescence quenching of salicylic acid in water.

Delayed lanthanide luminescence sensing of aromatic carboxylates using heptadentate triamide Tb(III) cyclen complexes: the recognition of salicylic acid in water.

The coordinately unsaturated terbium complexes Tb.1 and Tb.2 possess two labile metal-bound water molecules that can be displaced upon metal chelation to aromatic carboxylic anions such as salicylic acid in water, which gives rise to large enhancements in the Tb(III) luminescence.

Enhancement of the photocatalytic activity of TiO 2 film via surface modification of the substrate

A new type of TiO 2 film is prepared by insertion of a bifunctional silane agent bearing sulfonate group in between TiO 2 and the substrate. The alkoxyl silane is bound to the surface of the substrate via molecular self-absorption and the terminal sulfonate group is used to grasp the TiO 2 particles to form stable film. Modifications of the TiO 2 catalysts, such as metal deposition and calcination, were carried out simply with the films on substrates. The activity of this new type TiO 2 film is tested by catalytic photodegrading of salicylic acid in water. It was found that when the particle size of the TiO 2 is smaller than 200 nm, the catalytic activities of the TiO 2 films deposited on sulfonate-grafted glass are better than those of the films deposited on unmodified glass. Increasing the crystallinity of TiO 2 particles, depositing the precious metals (such as Au or Pd) on TiO 2, or aging the TiO 2 film will enhance the catalytic activity of TiO 2. The enhancement is better for the film deposited on sulfonate-grafted substrates. In spite of calcining the TiO 2 film decreased its catalytic activity due to the particle aggregation, the decrease is also less significant for TiO 2 films deposited on sulfonate-grafted substrates. The sulfonate group can be regarded as a dispersion agent for TiO 2 film deposition and calcination.

Concerning the role of oxygen in photocatalytic decomposition of salicylic acid in water

The photocatalyzed oxidation of salicylic acid on pure TiO 2 and ZnO films as well as on TiO 2 films loaded with various amounts of ZnO in N 2O-saturated aqueous solutions has been investigated. It was found that the photoassisted decomposition of salicylic acid did not take place on the irradiated surface of pure TiO 2 and took place on ZnO when N 2O was bubbled through the solution. The deposition of a small amount of ZnO onto the TiO 2 surface was responsible for the appearance of marked photocatalytic activity of material. The information about the electron-scavenger ability of N 2O in interaction with TiO 2 has been obtained by conductivity and photoconductivity measurements. The main conclusion is that the major role of oxygen in photocatalytic oxidation of organic compounds is to be a scavenger for continuous electron removal from photocatalysts.

Association, dissociation and hydrogen bonding of salicylic acid in water— N,N-dimethylformamide mixtures

The free energy of transfer (Δ G tr) of salicylic acid from water to N,N-dimethylformamide (DMF) and their mixtures was calculated from the solubilities of salicylic acid in different H 2O—DMF mixtures. The maximum value of Δ G tr was found to be −7.008 kcal for pure DMF. In addition to Δ G tr calculations, the values of the association constant ( K ass) of salicylic acid were calculated from the acid concentration (solubility, S) and the pH values of the saturated solution. The highest K ass value was found to be 1016.16 in pure DMF. Moreover, the free energies of H-bonding of salicylic acid in these mixtures were calculated from the values of Δ G tr and its individual terms (Δ G sum).

A Luminescent Probe Study of Water/Acetonitrile Mixtures

Luminescence spectra for 1.0 × 10-2 mol dm-3 solutions of salicylic acid in water, acetonitrile and water/acetonitrile mixtures have been determined. In the wavelength range 300-600 nm, all spectra showed a single broad emission band. The variations of the wavelength of maximum luminescence intensity (λmax) and luminescence band half-width (Δ�) with solvent composition are similar to the composition dependence of these parameters observed previously for solutions of salicylic acid in water/alcohol mixtures. The invariance of Δ� with acetonitrile content up to approximately 15 mole% supports earlier conclusions that up to c. 15 mole% acetonitrile is accommodated within cavities in the water structure. The rapid increase in near 15 mole% acetonitrile provides further evidence for a progressive destruction of the water structure as the acetonitrile content is increased beyond c. 15 mole%.

Determination of the Dissociation Constants of Salicylic Acid in Water-Ethanol Mixtures by Modified Conductometric Methods

Abstract The dissociation constants of salicylic acid in water and ethanol-water mixtures (8–87.6 wt % of ethanol), have been determined by the modified conductometric method as suggested by Gelb. The results have been checked independently from the plot Λ C vs. 1/Λ of salicylic acid in mixed solvents. Λ°HCIO4 and Λ°salicylic acid have also been determined.

Solubilization of Salicylic Acid by Polysorbate 80 as Determined by Solubility Titration

A solubility titration has been used to study the solubilization of salicylic acid in water by polysorbate 80 since a liquid phase separates from supersaturated solutions to give a distinct turbidity end point. The ratio of solubilizate to solubilizer necessary for complete water-miscibility was also determined. The method should be of general applicability in studying phenols solubilized by polyoxyethylene surface-active agents. The effect on the system of including a fixed weight fraction of certain additives in the polysorbate 80 was investigated. The additives included a series of monohydroxy alcohols of decreasing dielectric constants, a group of poly-hydroxy alcohols, polyethylene glycol 400, and Tween 20. Added monohydroxy alcohols increased or decreased the solubilizing power of polysorbate 80 in order of their polarity. Added polyhydroxy alcohols and polyethylene glycol 400 showed little effect. Added Tween 20 decreased the solubilizing power of polysorbate 80 in a linear fashion.