"do like you oughta, add acid to water" is an old saying in chemistry classes. You always pour any acids into water rather than vice versa because it's much more likely that the liquid being poured into will splash out of the beaker and get on your clothes. If it's just water, then no matter; but if acid gets on your clothes you'll have holes in your shirt for the rest of the day and you'll feel silly.

Yes, indeed. The worst laboratory accident I've ever witnessed happened when a student failed to follow this simple rule, though it was made far worse than it should have been by mistakes on the part of the school administration.

I was taking organic chemistry during the summer semester at my undergraduate college. The university administration, in its infinite wisdom, decided to cut costs that semester by doubling up the organic chemistry labs and by cutting back on air conditioning the science building.

Bear in mind that we were in West Texas. In July. It was ninety degrees outside, and there were thirty of us packed in a lab built for twenty with Bunsen burners going all the time. It must have been close to 115 degrees Fahrenheit in that lab.

So, we were wearing our safety goggles, yes. But almost everyone was wearing short-sleeved shirts, and many kids were wearing shorts.

One day, a student was at the crowded fume hood trying to mix hydrochloric acid and water. He made the mistake of pouring the water into the acid. He made a bigger mistake when, after the mixture started to spatter and smoke, he panicked and pushed the big reagent bottle away from him.

The huge bottle of hydrochloric acid fell over, sending an equally-huge splash of acid over a knot of about a dozen students nearby. A girl who was wearing shorts got acid all down the backs of her legs; she was in bandages for weeks afterward. I don't know anyone in the room who didn't find holes in their clothing from splashed acid afterward.

When things settled down, we learned an important sub-lesson: cotton protects you from acid much better than nylon or polyester. The people who were wearing cotton got holes eaten in their clothes but not their skin. The people who were wearing synthetic clothes that got soaked got burned.

Anyhow, I'm still amazed none of the injured kids sued the school. The next day, we were separated into two different labs, and the building was cooled to nearly arctic levels so that we could wear long pants and long-sleeved shirts without fear of getting heat stroke.

We were told:

Here lies Gillian, still and placid;
Who added water to the acid.
Clever Jane did as she oughter;
Added acid to the water.

And the reason for doing this is not simply to do with splashing, per se: If you add water to acid, the first drops of water will react completely and exothermically with the acid, very likely boiling it. If, on the other hand you add the acid to the water, the acid reacts completely with the water, and dissipates.

Ah, dearie me, this is fast developing into a chemistry-nerd's version of a GTKY node.

Even so, I cannot help but add my own little coda:

In Denmark, the following rhyme (usually sung to the tune of the ouverture to the Danish operetta Elverhøj) is used:

Gamle onkel Augustin
Han lever ikke mere
Han tog fejl af H2O
Og H2SO4

Which translates (roughly - I've tried to keep to the meter) as:

Dear old uncle Augustine
He walks no more among us
He confused the H2O
With H2SO4

I don't know the origin of this phrase, but it's at least half a century old, since it occurs in memoirs from the 1950s.

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