What combinations of clear, non-toxic chemicals create a colourful result?

July 3, 2009 4:17 PM

What combinations of colourless non-toxic substances result in something that's coloured, or at least opaque?

Aside from enzymes and substrates, are there any safe organic and/or inorganic clear substances that are known to change colour in the right combination? I vaguely remember doing things like this with a childhood chemistry set, but can't remember the specifics.

posted by greatgefilte to science & nature (4 comments total)

Ouzo and water mixed together become milky white: it's the ouzo effect.
posted by carmicha at 4:36 PM on July 3 [1 favorite has favorites]

Safe is relative, but sodium carbonate + phenolphthalein (in clear alcohol) turns reddish pink. Thymolphthalein (also in alcohol) + sodium hydroxide comes out garishly blue.

Sodium hydroxide is pretty caustic. The rest isn't too nasty.
posted by rokusan at 4:45 PM on July 3

Phenolphthalein is colorless in acidic solutions and is a light pinkish in basic solutions. I don't know what you mean by safe...just that you wouldn't want to ingest phenolphthalein given its historical use as a laxative.
posted by Captain_Science at 4:48 PM on July 3

Tonic water will fluoresce under a blacklight.
posted by pseudostrabismus at 8:22 PM on July 3