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Irradiation of an aqueous solution of the trans-isomer of disodium 4,4'-diacetamidostilbene-2,2'-disulfonate causes isomerization to the cis-form, reduction to the corresponding 1,2-diphenylethane, and oxidative cleavage to the corresponding aldehyde and carboxylic acid. When applied to wool prior to irradiation, the same products are formed, but in different proportions.

The colorimetry of specimens containing fluorescent whitening agents (optical bleaches) requires an illuminant with adequate ultra-violet content to at least 3600 A. Single sources based on the filament lamp have, generally, a low ultra-violet content. The use of two sources, one equivalent to Illuminant C provided by a filament lamp screened with an O.B. 8 filter, and the second the same lamp screened with an O.X. 1 or modified O.X. 1 ultra-violet filter, is suggested as giving a satisfactory approximation to the daylight spectral distribution, both in the visible and in the ultra-violet regions.

A spectral study has been made of the interactions of four types of fluorescent whitening agents with wool. Fluorescence excitation and emission spectra have been measured in single wool fibres, and are compared with the corresponding spectra in solution and in polymer films. The polarity of the environment has a pronounced effect on the fluorescence properties of the whiteners in solution, but generally has little effect in rigid media. The emission spectra in wool are found to be strongly influenced by the concentration of whitener in the fibre. This heterogeneity of the fluorescence is attributed both to aggregation of the whitener and to changes in the polarity of its micro-environment in the fibre. The results of fluorescence depolarization studies indicate that electronic energy transfer between whitener molecules occurs efficiently at the concentrations normally used for whitening wool. Critical transfer distances and concentrations have been determined for the various whiteners, and are compared with the values predicted by Forster's theory of dipole-dipole transfer. The photochemical behaviour of the fluorescent whiteners in wool has been examined, and the effects of oxygen and water on the fading rates are discussed.

This study is concerned with the physico-chemical background to the substitution of phosphates in laundry detergents, with special emphasis on combinations of zeolite A with other detergent ingredients, especially water-soluble cobuilders and optical brighteners. The most important action mechanisms of zeolite A / cobuilder systems were investigated for a variety of washing conditions. It is shown that the builder performance of zeolite A is often reinforced by small amounts of water-soluble substances such as polycarboxylates. These detergents are able to compete, in terms of performance, with products containing a high proportion of phosphate. Further, the interaction of zeolite A with fluorescent whitening agents in detergent powders was studied. It is shown that the photophysical properties of a typical optical brightener are negatively influenced by ionic builders and surfactants. In contrast to sodium triphosphate, zeolite A can enhance the appearance of powders even in the presence of anionic surfactants.

From the collection of toxicologic data, it is seen that the fluorescent whitening agents are a well-investigated class of compounds. Only in one of the groups of compounds investigated did it appear advisable to discontinue the use of a particular product on the basis of the toxicologic findings. In the large number of the other cases, the findings indicate that there is a considerable degree of toxicologic safety in the use of the FWAs in soap and detergent products.

The surface chemistry of eucalyptus pulp fibers prior to and after low-consistency (LC) refining was studied using a state-of-the art laboratory refining device and advanced surface analysis techniques. It was found that LC refining could generate fines and fibrillation and change the surface chemical composition of fiber surfaces. Both of these two effects can facilitate the adsorption of fluorescent whitening agents (FWAs) by the combination of increased specific surface area, electrostatic forces, and hydrophobic interactions, thus compensating for the loss of optical properties resulting from LC refining. The mechanical hydraulic force generated by the high refining energy disturbed the FWA retention. Therefore, high refining energy could improve the adsorption of FWAs when they are added after refining, but for better performance, the refining energy should be controlled and lowered. In addition, small amounts of calcium salt added after refining can also ameliorate the adsorption of FWAs.

The adsorption of two widely used fluorescent whitening agents (FWAs) on unbrightened cotton fabrics has been investigated as a function of temperature, hardness of the wash liquor, initial concentration of FWA in solution, and fabric to wash liquor ratio. Sorption efficiencies of FWAs have been studied using a UV spectrophotometry technique. A mechanistic model has been developed to describe the dissolution process of FWAs, convective mass transport into the fabrics, diffusion in the stagnant layer to the fabrics' surface, and adsorption of FWAs on cotton fabrics. Dual porosity of the fabrics (inter-yarn and intra-yarn porosity) has been considered by allowing two different regions (outer and inner areas of the cotton fabrics) where FWAs molecules can diffuse and adsorb. Good agreement between experimental and predicted whiteness benefit by the proposed mathematical model has been observed for the range of variables considered. © The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of 2017 American Institute of Chemical Engineers AIChE J, 64: 1305–1316, 2018

The analytical method of fluorescent whitening agents (FWAs) in river waters was examined. Two types of FWAs were identified qualitatively in river waters with the aid of the extraction method developed in the present work and thin layer chromatography.

To the Editor.— At a time when the number of new chemical formulations for products that have contact with the skin is increasing rapidly, a review for dermatologists of the nature of such chemicals by research staff members of producing companies is indeed pertinent. The article "Fluorescent Whitening Agents" by J. Griffith, PhD, 1 fulfills this need. Certainly, intensive clinical evaluation prior to marketing should be mandatory for chemical agents designed for widespread use. The Food and Drug Administration is doing a sterling job in prophylaxis and consumer protection by regulating the drug and chemical companies, both prior to and after introduction of new chemical agents. For example, the periodic evaluations of various topical germicidal agents made by the Antimicrobial Review Panel are most laudable. Griffith uses accepted predictive maximization procedures in attempts to contact-sensitize humans to a variety of fluorescent whitening agents (optical whiteners). He concludes that the

Fluorescent whitening agents improve the appearance of cloth or paper through two separate visual effects, a bluing effect and a lightening effect; the former is much more important than the latter. For any one shade of whitener, both the bluing and lightening effects are directly proportional to the effective fluorescence (defined here as the sum of the tristimulus values of the fluorescent light from the dyeing). However, when whiteners of different shades are compared at the same effective fluorescence, the greener-shade whitener has more of a lightening effect, but the redder-shade whitener has more of a bluing effect. These two advantages, one for the greener shade and the other for the redder shade, almost exactly cancel each other, so that at the same effective fluorescence both whiteners improve the cloth to the same degree. Effective fluorescence, as here defined, is therefore a reliable indication of whitening power irrespective of shade. This quantity may be measured on a fluorimeter, but an appropriate correction factor must be applied when two different whiteners are being compared.

Simulated solar irradiation of wool, silk, bovine serum albumin and apomyoglobin in the presence of radioactively labelled fluorescent whitening agents of the bistriazinylaminostilbene and pyrazoline types results in the irreversible binding of radioactivity to the protein. This photochemical reaction occurs both in the solid state and in aqueous solution, and is believed to result in the formation of a covalent bond between the whitener (or a photodecomposition product) and the protein.

Thirty-one fluorescent whitening agents (FWAs) that were considered for use in laundry products have been patch tested for skin-sensitizing potential. Test exposures were highly exaggerated over those anticipated for consumers. Three of the products tested produced delayed contact hypersensitivity under the test conditions, and they were accordingly rejected for consideration as detergent components. The sensitizing potential of two of these materials was tentatively attributed to a single chemical species that was present in both products. The other 28 of the materials tested gave negative test results and were judged to be very unlikely to cause dermatitis under practical usage conditions. For some of the materials, this prediction of safety has been validated by extensive market experience. All of the FWAs tested are identified by chemical names and structures.