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Domingos Lusitaneo Pier Macuvele Gerre Zebedias Samo Sithole Karina Cesca Suzana Lília Pinare Macuvele Jonas Valente Matsinhe 《Environmental science and pollution research international》2016,23(12):11639-11644
Indicators are substances that change color as the pH of the medium. Many of these substances are dyes of synthetic origin. The mulala plant (Euclea natalensis), which roots are commonly used by rural communities for their oral hygiene, and roseira (Hibiscus rosa-sinensis), an ornamental plant, are abundant in Mozambique. Currently, synthetic acid-base indicators are most commonly used but have environmental implications and, on the other hand, are expensive products, so the demand for natural indicators started. This study investigated the applicability of aqueous extracts of H. rosa-sinensis and E. natalensis as acid-base indicators. Ground on this work, the extracts can be used as acid-base indicators. On the basis of the absorption spectroscopy in both the UV-Vis region and previous studies, it was possible to preliminarily pinpoint anthocyanins and naphthoquinones as responsible for the shifting of colors depending on the pH range of aqueous extracts of H. rosa-sinensis and E. natalensis. These natural indicators are easily accessible, inexpensive, easy to extract, environmentally safe, and locally available. 相似文献
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Out of three perceptual characteristics of the colour of any substance, the hue depends mostly on the spectral properties
of a substance, while the brightness and saturation depend also on the concentration of a substance and its thickness. Here,
we report that evident change of the hue of the colour (i.e., from green to red) is due to a change in concentration or the
thickness of a layer in some exceptional substances such as pumpkin seed oil or an aqueous solution of bromophenol blue. In
some regions of Central Europe, salad dressing is made preferably with the pumpkin seed oil, which has a strong characteristic
nut-like taste and remarkable properties of the colour: it appears red in a bottle, but green when served as a salad dressing.
The colour of the pumpkin seed oil was previously described as brownish yellow, dark green, dark green to red ochre or dark
reddish brown to light yellow green. We elucidated the physicochemical and physiological basis of such dichromatism by Beer-Lambert
law and by the characteristics of human colour perception. Our concept was corroborated by the outcome of calculations of
colour from spectral properties using colour matching functions. We found that dichromatism is observed if the absorption
spectrum of any substance has at least two local minima: one wide but shallow and one narrow but deep local minimum. 相似文献
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Vidović Kristijan Hočevar Samo Menart Eva Drventić Ivana Grgić Irena Kroflič Ana 《Environmental science and pollution research international》2022,29(31):46405-46437
Environmental Science and Pollution Research - Atmospheric gases and particulate matter (PM) in contact with the material’s surface lead to chemical and physical changes, which in most cases... 相似文献
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