The content of vitamin C

Autumn is inseparably linked with the processes of harvesting, fruits and vegetables, nutrition that enriches the body with various vitamins, especially vitamin C. Probably everyone is interested to know what vitamin C content in freshly picked fruits and in those fruits that were stored for a week, a month, half a year, as the harvest of the last year to spring loses a significant part of vitamin C. This is due to the fact that vitamin C (ascorbic acid) is very unstable and easily oxidized by air oxygen, thus turning into another acid - dehydroascorbino th. Let's try to determine the content of vitamin C in an apple, lemon or orange, which we want to eat. This experience is useful for practical purposes. For example, how to determine the minimum amount of plant food that would completely satisfy you and your family members in vitamin C, the daily requirement of which should not be less than 70 mg. In addition, it is curious to know how the content of vitamin C in the juice varies with its heating.

Autumn is inseparably linked with the processes of harvesting, fruits and vegetables, nutrition that enriches the body with various vitamins, especially vitamin C

In our experiment, we will oxidize ascorbic acid not with oxygen, but with iodine contained in iodine alcohol tincture, which can be bought at a pharmacy. If it says 5%, it means that 100 ml contains exactly 5 g of iodine. For our experiments, iodine tincture should be diluted 50 times with water, obtaining a 0,1% solution. In addition, you will need a weak starch paste, which can be prepared as follows. Dilute a gram of starch into a small amount of cold water, and then pour it into a glass of boiling water. Blend the mixture on low heat for a minute or two.

Everything is ready, but first we will practice. Take a tablet of ascorbic acid, weighing half a gram. Dissolve it in 600 ml of water. Pour exactly 25 ml of solution. Dilute it with 100 ml of water. In the resulting weak solution of ascorbic acid, add 3 ml of starch paste and mix thoroughly. And now, gently, drop by drop, add a solution of iodine tincture to the usual pharmacy pipette. Do not forget to shake the contents. Read the drops and watch out for the color of the solution. When iodine oxidizes all ascorbic acid, its next drop will color the solution blue. This concludes the training.

Using the same pipette, we determine the amount of iodine tincture used in the experiment. Count how many drops are contained, for example, in 100 ml. Knowing the volume of the drop, you can fairly accurately determine the amount of iodine tincture used in the test. Using the reaction equation given in the figure, and knowing the concentration of iodine tincture, determine how much ascorbic acid was contained in the tablet. It should be that 50 ml of 0,1% solution neutralizes about 35 mg of ascorbic acid.

Now you can determine the content of vitamin C, for example, in an apple. To do this, weigh the apple on a laboratory scale and cut it in half. Cut one slice from one of the halves. To do so it is necessary because the content of vitamin C over the cross section of the apple is distributed unevenly. Put the lobster in a porcelain mortar and add a little starch paste, dilute hydrochloric acid and carefully pestle with a pestle. After this drop by drop add a solution of iodine tincture. The appearance of a blue color indicates that ascorbic acid is completely neutralized.

Now we need to know the mass of the sample. Weigh the remaining slices of apple. The difference in weight of the whole and both lobules will show which part of the apple went to the experiment. Then do as you did in the training experience.

The accuracy of this method is quite high. For example, in hips, the vitamin C content was determined to be 3,8% (according to tabular data in hips, the vitamin C content ranges from 2,7 to 5,3%).

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