Salicylic acid solutions

I. The amount of glacial acetic acid used may not be sufficient to dissolve completely the salicylic acid. Solution will... 

Discussion. Salicylic acid and iron(III) ions form a deep-coloured complex with a maximum absorption at about 525 nm this complex is used as the basis for the photometric titration of iron(III) ion with standard EDTA solution. At a pH of ca 2.4 the EDTA-iron complex is much more stable (higher stability constant) than the iron-salicylic acid complex. In the titration of an iron-salicylic acid solution with EDTA the iron-salicylic acid colour will therefore gradually disappear as the end point is approached. The spectrophotometric end point at 525 nm is very sharp. 

Salicylic acid solution. Prepare a 6 per cent solution of salicylic acid in acetone. 

Table 6.2 Formulations of salicylic acid salicylic acid solutions...

Salicylic acid USP, EP, and other pharmacopeia grades are used medically as antiseptic, disinfectant, antifungal, and keratolytic agents. Salicylic acid is formulated in lotion or ointment formulations for the treatment of dandruff, eczema, psoriasis, and various parasitic skin diseases. Because the keratolytic property of this aromatic acid has use in the safe removal of dead skin cells from the surface of healthy skin, the acid is used in concentrated salicylic acid solutions or suspensions to remove warts and corns. In more dilute form, salicylic acid preparations have found use in dandruff and eczema treatment. Salicylic acid has been considered and found effective by the Advisory Committees to the FDA in various over-the-counter (OTC) drug regulated uses. Among these are acne products, dermatitis, dry skin, dandruff and psoriasis products, and foot care products (24). 

Self-Diffusion Experiments. Diffusion was measured in a U-tube cell constructed in halves which could be clamped together with the disk or skin separating the arms of the U. Cells were secured on the arms of a shaker in a thermostat bath. Unlabeled aqueous salicylic acid solution (3... 

SALICYLIC ACID AND RELATED COMPOUNDS. [CAS 69-72-7], Salicylic acid or C H4(OH)(COOH) is a white solid, melting points 159°C, sublimes at 76°C, insoluble in cold water, soluble in hot water, alcohol, or ether. With ferric chloride solution, salicylic acid solutions are colored violet (distinction from benzoic acid). 

A reactor was charged with the Step 2 product (3.5 mmol), triethylene glycol (4.95 mmol), triethylene glycol monoglycolide (0.05 mmol), and 5 ml of THE. The mixture was then polymerized using salicylic acid solution in THF as catalyst. After 30 minutes 0.1 ml of triethylamine was added, and the product was isolated in 99% yield after the mixture was concentrated. 

Calculate the volume of 0.1 N salicylic acid solution required, taking into account the water content, w of the product to be tested, with the following formula ... 

Transfer the calculated volume of 0.1 N salicylic acid solution to the conical flask, close and shake vigorously for 5 min at 23-25°C. Fill the resulting suspension non-quantitatively into centrifuge tubes, and centrifuge for 10 min at 4000 rpm. 

To obtain the 100-% value, titrate exactly 20 ml of 0.1 N salicylic acid solution against 0.1 N sodium hydroxide solution in the same manner (titre in ml = T). 

Another spectrophotometric determination of salicylic acid in pharmaceutical formulations using copper acetate as a color developer. Different vol. of salicylic acid solution (10 mg/ml) were mixed with an equal vol. of copper acetate solution and made up to 10 ml with Na acetate acetic acid buffer (pH 5.6 to 6.0). The absorbance of the stable, yellowish-green complex was measured within 30 h at 730 nm (24). 

A typical example of a limit test is the test for salicylic acid in a sample of Aspirin BP. Salicylic acid is formed by hydrolysis of aspirin (or may be an impurity from the synthesis). The test involves comparing the violet colour produced when the sample is reacted with ferric chloride with that obtained from a standard salicylic acid solution. 

Buffer solution, 0.1 mol L i NH4+ /NH3 at pH 8.5, was used to produce analytical signal in the FIA system Salicylic add was provided from Merck (Darmstadt, Germany). Standard salicylic acid solutions were prepared daily by dissolving the appropriate amoxmt of salicylic acid in an ethanokwater mixture (30 70). The reagent carrier solution was composed of 2xl0 6 mol L i salicylic add and 0.1 mol NH4+ /NHs buffer solution (90 10) at pH 8.5. 

The catalytic efficiency of the Ti02/montmorillonite was tested on the photooxidation of salicylic acid. A photocatalyst suspension (0.1 wt/vol%) was prepared in 0.15 mM salicylic acid solution. Irradiations for 1 h were performed and samples were withdrawn after 5, 10, 20, 30,40, 50 and 60 min irradiation. Aliquots of the samples irradiated for various durations were centrifuged and particles interfering with photometry were removed by filtration through a sieve with 0.2 ptm pore size. Changes in salicylic acid concentration taking place as the reaction progressed were monitored by spectrophotometry at 297 nm (Fig. 3). The initial equilibrium concentration of salicylic acid was lowered by the adsorption of molecules on the oxide surface before irradiation [see the difference... 

Fig. 3 UV-VIS spectra of the salicylic acid solution during UV-irradiation using TiO2/M/H50 photocatalyst (csa,o = 0.15 mM, 0.1 wt/vol% catalyst content)...

Dissolve 1 g of salicylic acid in 60 ml of ethanol, adjust the volume to 100 ml with water dilute 10 ml of this solution to 1 litre as a standard, making 1 ml = 0-1 mg of acid. Dissolve 0-6 g of aspirin in a measuring cylinder in 9 ml of ethanol and dilute with water to 90 ml. Take two similar Nessler cylinders into one pour 60 ml of the solution, into the other the remaining 30 ml with 3 ml of ethanol and adjust to the volume of the first. There is thus a difference of 200 mg in the amount of aspirin in the two solutions. Add 1 ml of 1 per cent acid ferric ammonium sulphate solution to each, mix and match the colour by adding the standard salicylic acid solution from a burette. Each ml of standard is equivalent to 0-05 per cent of salicylic acid in the sample. 

Meier et al. combined the method described above with MBS to probe the soUd-liquid interface of a salicylic acid solution with AI2O3 in a proof-of-concept reaction system [28]. This was the first work to successfully use PM-IRRAS to simultaneously probe species both in the liquid phase and on the solid surface. The considerably lower concentration of surface species relative to a liquid phase over the solid presents many inherent challenges. Meier et al. used MBS to significantly reduce the detection limit. A solution of salicylic acid in cyclohexane was modulated with neat cyclohexane and the resulting data were deconvoluted. Meier et al. were able to differentiate between the surface acid and that in the bulk and found a longer phase delay for removal of the acid from the surface relative to removal from the bulk. 

Fig. 21.13. COD values vs. time of electrochemical treatment of salicylic acid solution with and without sulfuric acid (current density, 158 A m 2 temperature, 70°C).

Fig. 21.13 depicts the electrochemical treatment results for two salicylic acid solutions with and without sulfuric acid at 70°C at the same value of current density iappi= 158 A m ). Under these conditions, a more efficient elimination of COD was observed when the sulfuric acid was present. The comparison of the results obtained indicates that both homogeneous and heterogeneous AOPs occur when the solution contains sulfate ions. 

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