碘量法测维生素C

测量果汁中的抗坏血酸含量

Titrations Intermediate (High School) 40 分钟 ~$10.00

目标

以淀粉为指示剂，用碘量法测定新鲜果汁中维生素C（抗坏血酸）的含量。

背景

Ascorbic acid reduces iodine to iodide ions in a 1:1 molar ratio. Starch indicator turns dark blue-black in the presence of excess iodine. When all the vitamin C is consumed, the next drop of iodine produces the blue-black color, marking the endpoint.

安全警告

  • Iodine stains skin and clothing
  • Wear safety goggles
  • Handle iodine solution with care

所需PPE

goggles lab_coat

材料

  • Fresh orange juice (200 mL)
    Freshly squeezed preferred
  • Iodine solution (100 mL)
    0.005M
  • Starch indicator solution (10 mL)
    1% solution
  • Distilled water (200 mL)

设备

50 mL burette Burette stand and clamp 250 mL Erlenmeyer flask 25 mL pipette Pipette filler White tile

步骤

1

Rinse and fill the burette with the standardized iodine solution. Record the initial volume.

3 分钟 Iodine stains
2

Pipette 25.0 mL of orange juice into the Erlenmeyer flask.

2 分钟
3

Add 5 drops of starch indicator to the flask.

1 分钟
4

Titrate by adding iodine solution slowly while swirling. The brown iodine color will disappear as it reacts with vitamin C.

8 分钟
5

Near the endpoint, add drop by drop until a persistent dark blue-black color appears for 20 seconds.

3 分钟
6

Record the final volume and repeat for concordant results.

15 分钟
7

Calculate the mass of vitamin C per volume of juice. Compare with the labeled value.

5 分钟

预期结果

Fresh orange juice typically contains 40-80 mg of vitamin C per 100 mL. The starch-iodine endpoint should be a sharp transition to blue-black. Older or heat-treated juice will show lower vitamin C content.

清理

Dispose of iodine waste in designated containers. Rinse all glassware with water. Clean any iodine stains with sodium thiosulfate solution.

详情

类别
Titrations
难度
Intermediate (High School)
时长
40 分钟
预估费用
$10.00
步骤数
7
材料
4

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Frequently Asked Questions

What is the objective of 碘量法测维生素C?
以淀粉为指示剂，用碘量法测定新鲜果汁中维生素C（抗坏血酸）的含量。
How difficult is 碘量法测维生素C?
This experiment is rated as Intermediate (High School). It takes approximately 40 minutes to complete.
What safety precautions are needed for 碘量法测维生素C?
Key safety precautions include: Iodine stains skin and clothing; Wear safety goggles; Handle iodine solution with care.
What materials are needed for 碘量法测维生素C?
The main materials required are: Fresh orange juice, Iodine solution, Starch indicator solution, Distilled water.
What results should I expect from 碘量法测维生素C?
Fresh orange juice typically contains 40-80 mg of vitamin C per 100 mL. The starch-iodine endpoint should be a sharp transition to blue-black. Older or heat-treated juice will show lower vitamin C content.