E QUIPMENT REQUIRED Each student needs: Test Tube rack Test tube holder Test tube (4 in number)
MOLISCH’S TEST PROCEDURE Take 2ml of solution in a test tube. Add two drops of Molish’s reagent. Mix it well. Under the cooling conditions incline the test tube and add 2 ml concentrated H 2 SO 4 slowly along the sides of the test tube. Don’t mix the content
H 2 SO 4 is sulphuric acid. Sulphuric Acid is the most corrosive acid. This reaction is exo-thermic reaction. Acid and Water don’t go well together. Please be CAREFUL!!
BENEDICT’S TEST PROCEDURE Take 5ml of Benedict’s reagent Add 8 drops of solution to it. Mix well. Boil it for 2 minutes. Cool under tap water.
S ELIWANOFF ’ S T EST PROCEDURE Take 3 ml of Seliwanoff’s reagent. Add 3ml of carbohydrate solution. Mix well and heat for 3 minutes. Cool under tap water.
IODINE TEST PROCEDURE Take 2ml of solution in a test tube. Add 2 drops of iodine solution Mix well
As you get your results start writing your observation in the observation column. The principle and inference will be discussed at the end of the session. D OCUMENTATION Molisch's Test PrincipleObservationInference
B EFORE Y OU S TART Please button up your laboratory coats. Girls tie your hairs Check the temperature of the water bath. (>90) Cool for no more than half a minute under tap water.
P RINCIPLE O F M OLISCH ’ S T EST General test for carbohydrates Molisch Reagent composition : 5% alcoholic α- napthol. Carbohydrates in the presence of hot mineral acids undergo dehydration forming hydroxy - methyl furfurals. This condenses with α-napthol to form a purple ring at the junction of the two layers.
M OLISCH ’ S TEST ObservationInference A purple ring is observed at the junction of the two layers Indicates the given solution is a carbohydrate solution General test for carbohydrates
C ONTENT ’ S OF B ENEDICT ' S REAGENT Copper sulfate: provide cupric ions Sodium Citrate: Prevents the precipitation of cupric ions Sodium Carbonate: Provides an alkaline medium
P RINCIPLE OF BENEDICT ’ S TEST In an alkaline medium carbohydrates form enediols. Enediols reduce cupric ions to cuprous forming a colored complex. It is called as semi quantitative test which gives an approximate percentage of sugar present in the urine of a diabetic person
BENEDICT’S TEST ObservationInference Colour of the solution changes from blue to green, yellow, orange Indicates the presence of a reducing sugar.
INTERPRETATION OF BENEDICT’S TEST ColourPercentage of sugar Green0.5 (+) Yellow1.0 (++) Orange1.5 (+++) Red2.0 (++++)
I MPORTANCE OF THE B ENEDICT ' S T EST Used in the preparation of Urostix for diagnosing glucose in urine Used by Diabetics to check their glucose status.
P RINCIPLE OF S ELIWANOFF ' S TEST Seliwanoff's Reagent composition : Resorcinol in Concentrated HCL Principle: In acidic medium carbohydrates form furfurals which react with resorcinol to give a cherry red colour.
S ELIWANOFF ' S TEST ObservationInference Cherry red colour is observed Indicates the presence of a ketohexose i.e fructose.
P RINCIPLE OF I ODINE TEST Principle: Starch a polysaccharide forms a complex with iodine which gives a blue colour.
IODINE TEST ObservationInference Light blue colour is observed Indicates the presence of starch