Klarinet Archive - Posting 000460.txt from 1995/04

From: David Gilman <dagilman@-----.EDU>
Subj: H+/OH- Concentration in Saliva
Date: Wed, 26 Apr 1995 14:31:45 -0400

Regarding all this talk about phenolphthalein and other liquid indicators,
there is a much easier way to measure how acidic or basic your saliva is.
If someone you know has a chemistry set (or better yet a working
laboratory), get some litmus paper from him. Remember that litmus is reD in
aciD and Blue in Base. Thus, if your spit is acidic, it will turn blue
litmus paper red, and red litmus paper will not change color. If it's
basic, red litmus paper will turn blue; blue litmus paper will not change.
The stronger the acid/base, the more noticeable the color change will be.
If it's neutral, neither color litmus paper will change. Just place a
little saliva in a (preferably clean) shot glass and dip one end of the
paper into it. Saliva is already an aqueous solution (or arguably a
suspension); so, you shouldn't have to worry about dissolving it in anything.

If you want a more accurate test, use pH papers. They come in different
types for different pH (H+ ion concentration) ranges. All you need to know
to use these is that pH 7 is neutral. Less than 7 is acid; greater than 7
is base. The further away from 7 you get, the stronger the acid/base.
[E.g.: 8.5 is a weak base. 2.0 is a strong acid.]

So much for acids and bases. But, these are not the only components of
human saliva. Another important component is salivary amylase. This is a
digestive enzyme which begins the breakdown of carbohydrates in the mouth.
It works extremely well on starches and sugars, but ostensibly not at all on
wood. [If anyone wants to know why, I'll be glad to answer.] I don't know
if anyone has done any research on the action of salivary amylase on wood
(cellulose) fibers, but I have always been told that the effects are
generally not significant. What I would worry about is the corrosive action
of water itself, which is the major component of human saliva. Water,
especially when it moves, does wear substances down. Just look at polished
stones in a river to see an example. If it does that to a rock, think what
it can do to a beautiful piece of wood. And remember that molecules are
always in motion to one degree or another.

Of course, if the instrument gets too dry, the wood can change as well.
Wood does have a water content of its own. That's why it can change if it
is placed in a dry climate without adequate protection. But, a large amount
of water (either liquid or water vapor) can cause serious damage by
changing that internal concentration [this is why wood will swell or shrink
as humidity changes], or by dissolving some internal component of the wood,
or God knows what else.

The moral of the story is: keep the thing clean and dry. Listen to your
instrument. If the wood feels too dry, you need a humidifier or possibly
bore oil. If not, keep the water away from it. If you think your saliva
may be highly acidic or basic, try rinsing your mouth out with water before
playing, for water dissolves acids and bases. It dissolves sugars as well,
which could be even more damaging, depending on their concentration.

I feel better now. Those degrees in chemistry are actually paying off!

David Gilman