MINISTRY OF DEFENCE

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  MINISTRY OF DEFENCE. Establishment Of National University In Islamabad Total position. 29 Domicile , All over Pakistan    Qualification  intermediate to bachelor positions . Project Engineer(Civil) account Officer  supervisor assistant office boy     How to apply.   Apply online through the link https://www.fgei-cg.gov.pk/nup-rec.php   Last date to apply  02 April 2023. No TA/DA Fo Interview 
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Experiment 1 (Qualitative analysis of carbohydrate from unknown solution.)

OBJECT

Qualitative analysis  of carbohydrate from unknown solution.

CHEMICALS REQUIRED

H2so4(concentrated) 1% ethanolic alpha-nephthol and 2ml of original solution.

APPARATUS 

A Beaker, Test tubes, Stirrer, Volumatric flask.

PROCEDURE

Take 2 ml of unknown solution into the test tube and add 2 drops of 1% ethanolic alpha nephthol (Molish reagent) and shake the test tube.After the shaking mix well and add concentarated H2SO4 along the sides of the test tube ( approx 2ml) 
 
1)MOLISH TEST

Take 2 ml of unknown solution add 2 drops of 1% ethanolic alpha nephthol.Mix  well and add concentrated H2SO4 along the side of test tube
.
PRINCIPLE

The polysaccharides and disaccharides are hydrolyzed by concentrated H2SO4 into monosaccharides .The monosaccharides are dehydrated by the acid to form furfural or one of its derivatives. Furfural or its derivatives condence with alpha nephthol to form a violet colored complex


OBSERVATION 

Purple or violet ring appear at the junction of two layers 


https://youtu.be/zHcmxBi_wG0


RESULT 

 Carbohydrates present .

2) IODINE TEST ( Test for polysaccharides)

CHEMICAL REQUIRED

3 ml of unknown solution and iodine solution .

IODINE TEST 

Take 3 ml of unknown solution add few drops of iodine solution 

PRINCIPLE

The test depends upon the property of adsorption possessed by the large polysaccharides  molecules which adsorb the smaller iodine molecules on their surface to form a complex of ill defined chemical nature . The starch iodine ,dextrin iodine,and glycogen iodine  complexes are blue, reddish purple and reddish brown respectively. The properry of adsorption  decreases on heating, the complex dissociates and, therefore the color disappears.On cooling the conplexes are reformed, and the coloue reappears except in the case of dextrins.It has been suggested that heating produced a change on the surface of the dextrins molecules as a result of which they lose the property of adsorption .

OBSERVATION 

Blue colour appear 

RESULT

Starch present means polysaccharides are present.

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