Biology 1119 Organismal Physiology Lab Spring 2001

Lab 3: Ascorbic Acid Lab

1. Mixing the chemicals

A. Ascorbic Acid
- 4.0 mg/mL
- Keep cold and dark

B. DCIP

- 0.8g/L
- Store properly
- Dispose of properly
- Possible skin and eye irritant.

C. Metaphosphoric Acid

- 5% solution
- 5g in 100 mL
"pseudo" buffer
2. Other equipment

A. mortar/pestle
-To hold 100-mL
-Fill to about 20mL with metaphosphoric acid and10-20 grams Cabbage

B. Buret
- 50 mL buret
- Grease stopcock
- Use white paper to give clean background for titration.

C. Miracloth

- Filter with Miracloth
- Cut to fit funnel
3. Preparing the sample

A. About 10 grams of cabbage

- Get some leaves

B. Slice and dice into smaller pieces

-Cut small enough to be able to grind easily

C. Add some grit

-About 10g of Cabbage
-Metaphosphoric acid (~20mL)
-Sand

D. Grinding with metaphosphoric acid

- Grind well

E. Filter through miracloth

- Pour into miracloth lined funnel

F. Squeeze the cabbage juice out

- Squeeze cloth to extract fluid

G. The product

- About 20mL yield
4. Standardization

A. Mix the standard ascorbic acid with metaphosphoric acid

- Mix 9mL = 5% metaphosphoric acid
- 1 mL = of ascorbic acid (4.0mg/mL)

B. Fill the buret with DCIP

- Carefully fill buret with DCIP

- Leveled at 0 mL

C. Titrate

- Titrate standard

D. Notice Drip Color

- Will go from blue to pink to clear
-Expect 5 to 10mLs to do it

(mg/1mL) = (4mg(10) (dilution) /X mL (titrated))

if 10mL titrated then
40mg/10mL = 4mg/mL
5. Run a variable: boiled cabbage
- Boiling Cabbage

Do some calculations.