50.8 MB (3.9 MB compressed)
5166 x 3438 pixels
43.7 x 29.2 cm ⏐ 17.2 x 11.5 in (300dpi)
TURTLE ROCK SCIENTIFIC / SCIENCE PHOTO LIBRARY TURTLE ROCK SCIENTIFIC / SCIENCE PHOTO LIBRARY
Editorial use only.
Testing toothpaste for alkalinity. Litmus indicator changes its colour depending on the pH. Here a litmus indicator paper strip has changed colour from red to blue after coming in contact with toothpaste that contains sodium bicarbonate (NaHCO3). The test shows that the toothpaste is alkaline.
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