Determination of Mixed Phthalic Acid Isomers in Alkyd Resins

Abstract

must be used when a sample of an alloy containing silver chloride is first dissolved for analysis. In experiments in which pure silver chloride and synthetic mixtures containing silver chloride were treated with nitric acid under conditions simulating those that would be used for dissolving such an alloy, the loss of silver chloride was found to range from a minimum of 0.3 mg. to a maximum of 0 8 mg., with an average of 0 5 mg., the recommended correction. TEST 4YALYSESIn order to test Procedure I on an alloy of known composition, one &as prepared from 24-karat gold, fine silver of 99.99% purity, electrolytic copper, and reagent grade tin. These ingredients were weighed out on an analytical balance and fused in a graphite crucible under conditions that caused no loss of metal. Metallic lithium was used to deoxidize the melt which w:i* thoroughly stirred before being poured into a mold. Aftei removal of the rough surface metal, the ingot was reduced to chips in a milling machine, and these were thoroughly mixed to obtain the analytical samples. The calculated composition of the alloy is shown in Table I along with the results of duplicate analysis in which the gold and tin were separated and determined by Procedure I and the other components by conventional procedures. It will be seen t.hat the results for gold and tin are very satisfactory and those for t'he ot'her two metals acceptable.Procedure I1 was test,ed on intimate mixtures containing silver chloride t'hat were prepared from accurately weighed quantities of the several components. I t will be seen from Table I1 t,hat satisfactory results were obtained from the silver chloride as well as for the other components.The meta and para isomers of phthalic acid ha\e recently attained commercial significance in alkyd resin manufacture. An anal? tical method for measuring each of the three phthalic acid isomers in mixture consists of a special saponification technique to recover the acids from resin solution, followed by hydrolysis in methanol solution and measurement of the absorptitity at three ultraviolet wave lengths. Anal) tical control can be exercised on the new compositions.OR a number of years o-phthalic anhydride has been used F in the manufacture of alk?-d resins and these resins in paint.vehicles have been measured by determination of phthalic anhydride content. Recently, the nieta and para isomers, also known as isophthalic and terephthalic acid, have attained commercial significance and may be utilized in alkyd resin manufacture. Investigations were undertaken to determine the effect of these tbr-0 isomers on existing methods of analysis for o-phthalic acid and t,o devise methods of analysis for each isomer.Tivo quantitative methods for determining o-phthalic acid specifically in the presence of other dicarboxylic acids are found in the literature. In these methods, the phthalic acid is measured by its absorption in the ultraviolet region a t 2 i 6 mp (2) or by the weight of the lead salt formed in glacial acetic acid ( 3 ) . These two methods with sl...

Ultraviolet Absorption Spectra of Phthalic Anhydride and Related Substances. Analytical Method for Naphthalene and 1,4-Naphthoquinone

“…Even solid naphtho- 1,4-Naphthoquinone mainly at the surface, under the influence of daylight, and the color of the solutions changes from pale yellow to intense yellow and even to brown. These changes, however, are not so astonishing, as quiñones react photochemieally in various ways (7,(10)(11)(12)(13)(14)(15)(16)(17)(18). Neutral methanolic naphthoquinone solution was of interest in the analysis planned and was examined closely for light response.…”

Coatings

“…Interference from maleic and fumaric acids and nitrocellulose can be eliminated by a controlled potential electrolysis. Extension of the ultraviolet spectrophotometric method for determining phthalic anhydride in alkyd resins has been made (60) to obtain analysis of the three phthalic acid isomers in mixture. A slow saponification technique is employed to prevent excessive entrainment of soaps, the precipitated salts are dissolved in water, acidified in the presence of methanol, and absorbances are measured at 275, 281, and 287 my.…”

Polarographic Determination of Terephthalic Acid in Mixtures of Phthalic Acid Isomers

“…Swann and Adams (5) recently reported the use of infrared spectroscopy for the detection of phthalic acid isomers which could materially assist in quantitative analyses by subsequent methods such as ultraviolet absorption spectroscopy. A method based on ultraviolet spectroscopy was reported by Swann, Adams, and Weil (6) for mixtures of the phthalic acid isomers. The concentrations of the acids are calculated by simultaneous equations based on the absorptivities of the acids at certain wave lengths.…”