Ira Remsen's Investigation of Nitric Acid
A comical reenactment of Ira Remsen's experience with nitric acid.
In this classic demonstration, the experience Ira Remsen had with nitric acid can be reenacted. Ira Remsen (1846-1927) was an influential chemist in America. He founded the chemistry department at Johns Hopkins University and initiated the first center for chemical research in this country. In this experiment, he describes his experience with nitric acid.
Nitric acid reacts with copper to produce the brown gas nitrogen dioxide:
Cu(s) + 4H+(aq) + 2NO3-(aq) → Cu2+(aq) + 2NO2(g) + 2H2O(l)
500 mL Erlenmeyer Flask
5 mL concentrated 16M nitric acid, HNO3
Several damp, folded paper towels
Large piece of cloth on which a dropper full of nitric acid had previously been squirted
Pre 1982 copper penny.
It is suggested that one reads his account as one performs the demonstration:
"While reading a textbook on chemistry, I came upon the statement 'nitric acid acts upon copper." I was getting tired of reading such absurd stuff and I determined to see what this meant. Copper was more or less familiar to me, for copper cents were then in use. I had seen a bottle marked 'nitric acid' on a table in the doctor's office where I was then 'doing time!' I did not know its peculiarities but I was getting on and likely to learn. The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. Then, the statement, 'nitric acid acts upon copper' would be something more than mere words.
All was still. In the interest of knowledge I was even willing to sacrifice one of the few copper cents then in my possession. I put one of them on the table, opened the bottle marked 'nitric acid', poured some of the liquid on the copper, and prepared to make an observation."
1. Place the penny in the 500 mL flask.
2. Carefully add 5 mL of concentrated nitric acid.
3. Place several damp, folded paper towels over the top of the flask to dissolve the gas evolved.
"But what was this wonderful thing which I beheld? The cent was already changed, and it was no small change either. A greenish blue liquid foamed and fumed over the cent and over the table. The air in the neighborhood of the performance became dark red. A great colored cloud arose. This was disagreeable and suffocating - how should I stop this? I tried to get rid of the objectionable mess by picking it up and throwing out of the window, which I had meanwhile opened. I learned another fact - nitric acid not only acts upon copper but it acts upon fingers. The pain led to another unpremeditated experiment. I drew my fingers across my trousers and another fact was discovered. Nitric acid also acts upon trousers.
4. Display to the audience a large piece of cloth on which a dropper full if nitric acid had previously been squirted.
5. Add water to the nitric acid to stop the reaction.
6. Rinse the flask and remove the penny (now much smaller!)
"Taking everything into consideration, that was the most impressive experiment, and, relatively, probably the most costly experiment I have ever performed. I tell of it even now with interest. It was a revelation to me. It resulted in a desire on my part to learn more about that remarkable kind of action. Plainly, the only way to learn about it was to see its results, to experiment, to work in the laboratory."
Wear safety goggles. Use a face shield and gloves when using concentrated nitric acid. This demonstration must be done in a well-ventilated area or in the hood. NO2 is a toxic gas.
Neutralize acid with sodium bicarbonate and flush resulting solution down the drain with copious amounts of water.
1. This wonderful excerpt is taken from Getman, Frederick H., J.Chem.Educ. (1940), 9-10.
2. This demonstration is an excellent way to begin a course in chemistry - maybe have students learn more about Ira Remsen.
3. Considering when Ira Remsen did this "experiment", have students comment on his investigation.
4. Ira Remsen is the codiscoverer of the artificial sweetener saccharin.