In article ations,
Kevin Miller wrote:

Leo Lichtman wrote:
If you're a stickler for correctitude, make that HCl.

And if you dilute it, be sure to observe the safety rule of *always*
pouring the acid into water rather than the other way around.

That way, it will be the diluted acid that splashes or spills, not the
full strength...

The reason is a bit less obvious than that, as demonstrated in
high-school chemistry to make the point. At least back when I went to
high school it was - with all the skittishness about exposing young
persons to the faintest shred of real life, it's no doubt no longer in
vogue, regardless of proper safety precautions.

When you add water to acid, the water can be heated to boiling - I
forget the details of why, but I remember the effect. Effectively, you
can consider acid dilution to be an exothermic "reaction." The heat is
there in either direction, but the distribution of heat is significantly
different with acid to water .vs. water to acid. When water is added to
acid and the water flashes to steam, you get acid being flung out of the
container by the steam - not good.

Chemistry students who retained more are welcome to fill in the details,
or the web probably can as well. I don't need them, I recall the effect
and that's plenty for me.

--
Cats, coffee, chocolate...vices to live by