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# 1.1 Chemical reactions – a first-hand experience

This is an account from around 150 years ago when American chemist Ira Remsen discovered, in no uncertain terms, what chemical substances combining to form new substances – a chemical reaction – can mean in practice.

> While reading a textbook of chemistry, I came upon the statement, nitric acid acts upon copper, and I was determined to see what this meant. Having located some nitric acid, I had only to learn what the words act upon meant. In the interests 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 I prepared to make an observation. But what was this wonderful thing which I beheld? The cent was already changed, and it was no small change either. A greenish- yellow liquid formed and fumed over the cent on the table. The air became coloured dark-red. How could I stop this? I tried by picking up the cent and throwing it out of the window. I learned another fact: nitric acid acts on fingers. The pain led to another unpremeditated experiment. I drew my hands across my trousers and discovered nitric acid acts on trousers. This was the most impressive experiment I have ever performed. I tell of it even now with interest. It was a revelation to me. Plainly the only way to learn about such remarkable kinds of action is to see the results, to experiment, to work in a laboratory.

Chemists represent reactions by writing equations, and for Ira Remsen’s reaction this is as follows:

At first sight this may appear unintelligible, something akin to a foreign language, and that is essentially what it is. A chemical equation is written in a different language from that used for everyday communication. However the basic tools to enable you to unravel equations such as these are covered in Section 2.

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