In corn grain by Arkhypovych .

Instruments, laboratory glassware, reagents:

Saccharimeters, polarimetric cell length of 400 mm, weight specifications, water bath, volumetric flask 200 cm2, filter, paper, concentrated hydrochloric acid, dried phosphotungstic acid, powdered activated carbon.

Sample of crushed corn 15g (14,48 -normal sample) weighed on technical scales and transferred with distilled water in a flask { 200sm3. Add 45 cm3 of hydrochloric acid in a volume of 200 cm3) in; flask add about 180 cm3 of water and placed in a boiling water bath for 25 min.

After hydrolysis flask was rapidly cooled under the tap to 20 C, add water to the mark, mix, filter. Illuminate filtrate 0.3 g dry phosphotungstic acid and 0.25 g of dry activated charcoal for 5 minutes, filtered again. The filtrate polarizes in polarimetric cuvette at 400 mm. Prepared testimony polarimeter P1.

In parallel control experiment conducted for an amendment to the soluble carbohydrates.

The control experiment.

Weigh 15 g of crushed grain is transferred into the flask left for 20 minutes, the contents of the flask with distilled water adjusted to the mark, mix, filter. Sampling is 100 cm3 filtrate transferred into a flask of 200 cm3, 45 cm3 of HCl is added to the relative density of 1.19 to bring the volume to 180 sm3.Kolbu flask placed in a boiling water bath for 25 min. After hydrolysis flask was cooled to 20 ° C, bring water to the mark, illuminate 0.3 g dry phosphotungstic acid and 0.25 g of dry activated charcoal, stirred, filtered, polarizes in polarimetric cuvette at 400 mm. Prepared testimony polarimeter P2. Result transferred to a sample of the product taken in determining the line polarization as follows:

,

Where: P2 - sugar- readings at the last polarization, N - sample to determine the direct polarization 15g) ng sample in determining adjustments for vuhlevoly soluble (15 g), 2 - koefitststsi'ent taking into account the dilution of the sample. Locate a correction is subtracted from the polarization P3 P1 by direct hydrolysis:

P = P1 - P3.

Number starch as a percentage determined by the formula:

where: P = P1 - P3, ° L;

H - a sample of the product g (15);

0.2896 - conversion factor for the normal sample.

Sample.

For the analysis of a sample taken 15 g of corn gruel.

Indications sugar- scale:

Test solution 33.0, 33.5, 33.6, 33.2

Аналіз отриманих результатів

Студент повинен зробити висновки про методи підготовки проб. Визначте основні етапи проведення аналізу.

Запитання для самоперевірки

1. Яким вимогам має відповідати препарат підготовлений до поляриметричного аналізу вуглеводів?

2. Як проводиться метод визначення вуглеводів за методом Архиповича?

З. Дайте порівняльний аналіз визначення вуглеводів за методом Еверса та методом Архиповича?

Laboratory work 8

Дата добавления: 2015-11-14