Posts: 2
Joined: Sat Jul 31, 2004 9:57 pm

How to measure vit C please

Postby jdionora » Sat Jul 31, 2004 10:03 pm

May i please know how to do the titration technique with tincture of iodine, 2%. to determine the vitamin C from fruit juices. This was a sample project suggested by the science buddies with the title "C-trus Screening
Sample Chemistry Project"

Posts: 145
Joined: Mon Dec 08, 2003 5:46 pm

Postby shijun » Mon Aug 02, 2004 10:24 am


Here are a couple of links that will help you out:

http://www.stemnet.nf.ca/d6vsatf/s1/VIT ... aminC.html

Pay attention to the section titled Procedure in the second link (also copied below, 3 & 4 especially). You will do something SIMILAR.

Hope this helps!



1] Pour 15 mL of the vitamin C indicator into a 50 mL beaker or medicine cup.

2] Using a clean medicine dropper, add a drop of one of the orange juice samples to the indicator in the flask. Gently swirl the liquids to mix.

3] Continue to add orange juice, drop by drop, until the indicator changes from blue to colorless. Note: Be sure to swirl after each drop is added.

4] Observe and count the number of drops of orange juice you needed to add to the indicator to cause it to lose all of its color. Juices low in vitamin C will begin to dilute the indicator. The indicator will start to take on the color of the juice. If this occurs, indicate that no satisfactory end point was reached. Record the number of drops added in the chart on your data sheet.

5] Repeat step 4 two more times and calculate the average number of drops (to the nearest tenth) required to change the indicator.

6] Repeat the above steps for each orange juice sample being tested. Note: Be sure to rinse your medicine droppers between tests and to use clean containers for each trial!

7] Find out how much vitamin C the label claims is present in one of the orange juice preparations you tested. Record the milligrams of vitamin C and volume of juice you would need to consume in order to ingest that dosage. In other words, record the amount of vitamin C you get per serving and the size of the serving in ounces and milliliters (if available).

Posts: 2
Joined: Sat Jul 31, 2004 9:57 pm

Postby jdionora » Mon Aug 02, 2004 6:55 pm

Thanks guys for the Titration method to determine vit C!
-jacque & mikey

Return to “Physical Science”