Answer to Question #59902 in General Chemistry for Anika

Question

If I want to make a nail polish coating that indicates when it's been exposed to alcohol (such as when someone spikes a drink), how might I go about doing that? I was thinking I might be able to use a coat of shellac on top of some sort of indicator, since shellac only dissolves in alcohol and not water, but I'm worried that it might take too long to dissolve, in which case, are there any better coatings?

As for the indicator, the pH of various drinks is all over the place, and I'm afraid that the pH of a spiked drink may not be unique enough to be able to really tell if the drink has been spiked. If this is the case, is there some sort of other chemical reaction that would cause a change in color (or some other noticable indication of a change) when exposed to alcohol in the levels that would be in a spiked drink?

Answer 1

Shellac is well-soluble in alcohols. Therefore, it is a good idea to use it as a coating. Regular pH indicators will not be effective for alcohols. All of them show neutral reactions for alcohols. Alcohols don’t react with a change of a color with any known indicator. That is why most commonly alcohols are analytically determined by the gravimetric, refractometry or gas chromatography methods.