In this short video, I would like to demonstrate what alkalinity is.
So remember, a measurement of alkalinity in water can tell you how much acid or base can be absorbed
without changing the ph of the water. For this demonstration, I prepared two beakers with a
water sample. Beaker #1 contains only deionized water and Sample #2 contains deionized water,
and I dissolved a little bit of baking soda to it. This is just baking soda which you might
know - and baking soda chemically speaking, is sodium bicarbonate. So I dissolved a little bit of
it, so we have some bicarbonate in the water that contributes to the alkalinity of the water sample.
So what we're going to do now is, I will add drop by drop, a few milliliters of
regular vinegar to the water sample now. Vinegar is a little bit acidic, has a ph of approximately
three, and we will look what the ph of the water sample is doing while I'm adding it. So, I have
here our ph meter HQd, and you see the deionized water sample has a ph of approximately 5.5.
So now, I'm gonna drop a little bit of the vinegar to the water sample,
and let's see what the ph - how the ph is behaving. So I put one drop only.
Takes a few seconds, and you see already you have already a drop of a ph of 1 to 4.4
with only one drop of vinegar. So it reacts very quickly to the acid. I add another one,
second drop and the ph will further decrease
to a ph of 4 already. Yeah, so we started at 5.6 or
approximately and we are already at 4 with two drops of vinegar. I can add a third one,
the ph will drop a little further, but remember the vinegar itself
has a ph of approximately 3. So with three drops, we were able to decrease the ph from 5.6
to 3.9. Okay what I'm going to do now, is I will rinse the ph electrode.
Dry it a little bit with a soft cloth, and then I will put the other sample -
put the ph meter in. Let's see how the ph is stabilizing - that takes a few seconds.
So that is now deionized water with the sodium bicarbonate.
We let it stabilize for a few seconds.
So you see we are approximately at 7.4 or 7.3.
Yeah 7.2.
and now it's very close to showing a stable value. So we approximately had 7.1, and I proceed the
same way that I did with the previous sample and add some drops of vinegar. Remember I just added
three drops of vinegar to the previous sample, and the ph dropped significantly.
So we had 7.06 now, and I will drop - put a drop of vinegar to it. One drop.
It reacts a little bit, but not that much.
So we are still at 7. I put a third - a second drop sorry.
Now I put already three drops to it,
and you see the ph decreases a bit,
but not too much. Add some new drops,
add another two drops.
So decreases very, very slowly.
Another two drops.
You see there's almost no change in ph. That means there is something in the water
which absorbs the acidity from the vinegar, so that the ph cannot drop. So
that is why alkalinity is also referred to the buffer capacity of water,
because now the vinegar - or let's say the the alkalinity buffers the water, so that the ph
is not changing very much by adding an acid. Last time I add some drops - one, two, three drops.
And you see the ph is not changing very much. That was a short demonstration what alkalinity is.