Natural Buffers
Procedure:
1. Always wear safety goggles.
2. Rinse the beakers and the graduated cylinders in the sink.
3. • Measure 10 ml of water in the graduated cylinder marked
"water," and pour it into the beaker marked "water."
• Measure 10 ml of gelatin in the graduated
cylinder marked "gelatin," and pour it into
graduat ed
cylinder
the beaker marked "gelatin."
wat er
4. • Add 3 drops of universal indicator to each beaker.
• Gently swirl each beaker to mix.
gelat in
• Compare the color of each solution to the pH chart below.
ACID
pH scal e
chart
pH 4.0
NEUTRAL
pH 5.0
pH 6.0
pH 7.0
BASE
pH 8.0
pH 9.0
pH 10.0
pH is a measure of how acidic or basic a solution is.
5. Add 3 drops of sodium hydroxide (NaOH) to each beaker. Swirl to
mix. What color (how acidic or basic) is each solution now?
6. How many drops of sodium hydroxide would you need to add
to the gelatin beaker to make the solution turn purple?
Try it and see!
7. Rinse out the beakers and the graduated cylinders in the sink.
©2005 OMSI
What kept the gelatin
solution from turning
purple?
A Closer Look:
Gelatin, which is derived from animal bones,
contains special chemicals called buffers. Buffers
resist the effects of acids and bases, that is, they
help maintain pH (acid/base) balance.
Water, on the other hand, doesn’t have any
buffers, so it quickly becomes acidic when acid
is added. It also quickly becomes basic when
base is added.
Buffers are very important to living organisms, since life
must maintain a constant pH balance in order to
survive. When that balance is upset, natural buffers
such as gelatin react with the extra acid or base to
return the organism’s pH to the proper level.
Two important buffers in human beings are the carbonic
acid buffer system in our blood and the phosphate
buffer system inside our cells.
©2005 OMSI