Chemistry and Botany

I have read the praises of coffee grounds for plants. I read that it is good for hydrangeas to make the flowers blue an effect of vinegar, an acid. This lead me to wonder if coffee grounds were acidic.

In this WONDERFUL, INTRUIGING book, The Mystery of the Periodic Table, (a must read,) I had read how to tell acids from bases (the opposite of acids.) So I proceeded to do the test.

First, I boiled four purple cabbage leaves in four cups of water for fifteen minutes.

Boiling Cabbage

Boiled Cabbage Leaf

 This is what the leaves looked like when the where done

This is the water’s original color

Cabbage Water

Before I started my experiment, I first added things I knew whether or not they were acidic or basic. I put in acidic vinegar with a low Ph of 2 and the blackish-purple water turned red. I put in the slightly basic backing soda (with a Ph of 8) and the water turned slightly green.

These are the results of my experiment: When I put the cabbage water in the coffee grounds, expecting it to turn red, nothing happened! I tried it again with the same results! THE COFFEE GROUNDS WERE NEUTRAL! To confirm my results, I went on to the internet to find the Ph of coffee grounds. They have a Ph of 6.7, 7 being purely nuetral.

I read that coffee grounds making hydrangeas blue-er was a myth.

Cabbage Experiment

Left to right: Vinegar, Coffe Grounds, Baking Soda.


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