54.6 MB (579.5 KB compressed)
4370 x 4370 pixels
37.1 x 37.1 cm ⏐ 14.6 x 14.6 in (300dpi)
SCIENCE PHOTO LIBRARY SCIENCE PHOTO LIBRARY
Phenolphthalein acid-base indicator. Phenolphthalein indicator changes its colour depending on the pH (hydrogen ion concentration) of the solution, it turns colourless in acidic solutions (left) and pink in basic (alkaline) solutions (right).
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