Principle of Seliwanoff’s test
Seliwanoff’s test is used for difference between ketose and aldose sugars. It is for the detection of fructose i.e this test is positive for fructose and negative for other sugar. With the help of this test we can easily distinguish and detect fructose solution.
When the saliwanoff’s reagent is mixed with sugar solution, it will give color for keto group.
Reagents for seliwanoff’s test:
- Saliwanoff’s reagent (recicinal plus hydrochloric acid)
- Original solution
Procedure of Saliwanoff’s test:
- Take 3ml of salwenoff’s reagent in the test tube.
- Then add 3 drops of original solution in the test tube.
- Heat the mixture.
- If red colour appear, then it shows that keto group or fructose is present in the original solution.
Here are some of the things that you need to take care of while performing this test:
- Add seliwanoff reagent more then the solution as mentioned above in the procedure.
- Heat the solution carefully.
- Keep the test tube to side while heating. It should not be towards any human.
- Remove the test tube from fire when the solution boils the the opening of test tube. Place it again when it goes down.
Some important points about seliwanoff’s test:
Here are some of the important things about seliwanoff’s test that you must remember while performing the test:
- First polysaccharides or oligosaccharides are hydrolyzed to simple sugar by acid hydrolysis.
- Simple sugars then react with recicinal to produce deep red color.
- Aldose sugars will not react will recicinal and produce a faint pink colour.
- Recicinal reacts with only fructose and sucrose. (As sucrose contains fructose and glucose, seliwanoff’s reagent react with its fructose part).
- All other sugars except fructose and sucrose gives negative result with saliwanoff’s reagent.
If you follow the step by step procedure written above correctly keeping the precautions in mind then you would see the color of solution changing to red if your solution contains keto sugar.
You can also test it for aldose sugar and see yourself the negative results. It would produce a light pink solution as mentioned above.
pls I need discussion, conclusion and precautions on seliwanoff’s test for ketose
post updated for you…
pls sir… I have some questions.
state how to prepare the following solution
(1) 5% alpha naphthal in alcohol
(2) 0.005% in 3% KI
(3) 40% Naoh
how to prepare the following
(1) 35ml of 0.25M solutions of a compound with FW of 185g/ml
(2) 450ml of 14% Nacl in water
(c) 15ml of 0.05% AgNO3
convert the following solution
(1) 6.5% solution of a chemical with FW = 325.6 to a molarity
(2) 0.045 M of a chemical with FW = 178.7 to %
(3) 100Mm to u mol/ml
(4) 20 u mol/Litre to u mol/ml
question: you are given 100mg/ml of a stock solution and asked to make 200ul of 24mg/ml solution
(2) how many grams of solid Naoh are required to prepare 500ml of a 0.04M solution.
(3) express the answer above question 1 in Normality
sorry, these are out of topic questions. i am a medical student and don’t remember much of chemistry now. so its better to ask a chemistry teacher.
Salisu ktn says
Thank u admin
well would you please name some uses of seliwanoff’s test in pharmacy?
Abu nucman says
Could you please sir explain why seliwanoff’s reagent changes colour for ketoses and not aldoses