Author： Helseth L E
Publisher： IOP Publishing
ISSN： 0143-0807
Source： European Journal of Physics, Vol.32, Iss.5, 2011-09, pp. : 1193-1197
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Abstract
We propose a simple and fascinating experiment for studying diffusion in gels using a pH-sensitive dye. By doping agar with methyl red, we obtain a gel which rapidly reacts to changes in pH by changing its absorption spectrum. The pH gradients can be followed using a digital camera, and we demonstrate here that the pH-sensitive colour changes can be used to print colour patterns in the gel which due to diffusion of ions may disappear entirely.
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