Monday, June 4, 2012

Calcium Acetate or the Lemon Meringue Pie Effect

A while back I was working with some North Evans Limestone samples looking for conodont fossils. Dave at Views of the Mahantango blog had left me with some specimens to work with. He told me to dissolve the pieces in vinegar and then look for small fossils.  This worked (see pictures at bottom of post) and afterwards I left the samples in the sun room where I do most of my photography and microscope work.
Several weeks passed when I noticed something interesting in the container, formations of white crystals were forming. As it turns out a chemical reaction was taking place, one in which the limestone samples (calcium carbonate) were interacting with the vinegar (acetic acid) to form water, carbon dioxide, and calcium acetate (calcium salt). The carbon dioxide floated off into the atmosphere, the water eventually evaporated, which just left the limestone and crystallized calcium acetate.

Limestone + Vinegar =  Calcium Salt + Water + Carbon Dioxide

CaCO3 + 2CH3COOH = Ca(CH3COO)2 + H2O + CO2


The calcium acetate formed a texture and color that reminded me of the layer of meringue that one finds on lemon pies.


Lemon Meringue Pie - photo by Renee Comet (1994) - wikipedia.org
The last three pictures are of some Devonian Period conodont fossils I found in the limestone. Not sure of their names but if I had to guess maybe a Prioniodus sp. Learn more at the web site of North Evans Limestone fossils found at Penn-Dixie Cement Quarry in Hamburg, New York.


3 comments:

Tony Edger said...

Great post. Chemistry and microfossils -- an unbeatable combination for fun.

Dave said...

That is a very cool post, Mike. The reaction you are describing is the same one that they sell as "Popcorn Rock" in tourist shops. A chunk of limestone in a bag with instructions to leave it in vinegar for an extended period of time. Nice Conodont too!

Kentuckiana Mike said...

Thanks for the info. I wondered what "popcorn rocks" were.
The chemical formation was a unintended bonus.