Kitchen Science Write-up: The Sand of Sand Beach

A few months ago, I had the privilege to visit Acadia National Park on the coast of Maine.  Most of our stops at this preserved of unfettered nature, I confess, involved either ice cream or legions of people trying to sell us Acadia National Park licensed leisure wear in a faux-village setting, but we did also visit a small stretch of coastline called "Sand Beach."

The name "Sand Beach" would be a bit redundant where I come from, but apparently this particular beach is the only stretch of sand-like material for quite some miles, the local geology, currents, and tides not favoring the build-up of coarse silicates at the waters edge.  Indeed, said the interpretive material, the sand of Sand Beach isn't really sand per se, but mostly chunks of wave-battered seashell.  "Cool," thought I, and quickly gathered a sample.  (A few minutes later it would occur to me that one oughtn't take samples of relatively scarce materials in protected natural areas; my only defense is that I did what I did in the name of (kitchen) science.)

The Experiment

Back at the Castle5000 laboratories, the experiment was conducted as follows: a more or less equal amount of Sand Beach sand was placed in each of two teacups.  To one was added vinegar, whose acidic quality is often demonstrated by its amusing reaction when added to baking soda.  To the other was added a carbonated cola beverage, the corrosive power of which is legendary, albeit -- in my considerable experience -- entirely unreproduceable.

In the vinegar sample, a thin layer of bubbles appeared within minutes and would remain for the next two or three weeks:

My hypothesis is that the bubbles were the reaction of the acidic vinegar with the calcium carbonate in the shell fragments in the sand.  No such bubbles occurred in the cola sample, and although there were initially the same bubbles one would expect in any carbonated beverage these soon dissipated in the normal fashion.

At the end of approximately three weeks, there was a marked difference between the two samples:

At left, the vinegar sample, and at right the cola sample with unfortunate caramel color sludge.  Note that the volume of sediment is far less in the left-hand sample, and also that whereas the right-hand sample still contains many visible large white shell particles, the left-hand sample appears to be comprised of fine mineral particles.

CONCLUSIONS: Sand Beach really is mostly shells, although maybe not entirely shells like the literature suggested.  Vinegar is probably a lot more acidic and corrosive than cola.  It is fun to conduct little experiments, even if they make your lair smell like vinegar.

I did not use my entire supply of contraband Sand Beach sand in conducting this experiment, so follow-up experiments are possible and I would be happy to entertain suggestions from the floor.