Write the method of preparation of lassagine's extract
Answers
Answer:
Take a small piece of dry sodium in a fusion tube.
Heat the tube slightly on a Bunsen burner so that the sodium melts to a shining globule.
Add a pinch of the organic compound.
Heat it slowly to start with so that the compound reacts with sodium metal.
Now heat the tube strongly till it becomes red hot.
Plunge the red hot tube into a china dish containing distilled water.
Crush the contents with a glass rod and heat to boiling point.
Stop heating and remove the insoluble matter by filtration.
The filtrate is called Lassaigne's Extract.
Explanation:
Answer:
Lassaigne’s test is used to detect the presence of elements: Nitrogen (N), Sulfur (S), Chlorine (Cl), Bromine (Br) and Iodine (I). This test involves following two steps.
i) preparation of sodium fusion extract (SFE).
ii) Detection of elements using SFE.
Explanation:
(i) Preparation of SFE
A small amount of organic substance is fused with small quantity of sodium metal in a fusion tube. The red hot fusion tube is then plunged into distilled water and the contents are boiled for a few minutes, then cooled and filtered.
The filtrate obtained is called sodium fusion extract (SFE) or Lassaigne’s extract. It is usually alkaline. If it is not alkaline, a few drops of NaOH solution may be added to make it alkaline.
(ii)Detection of elements using SFE
Thus obtained SFE is used to detect the presence of elements like N,S,Cl, Br & I.
The elements in the organic compound react with sodium during fusion reaction as follows:
Na + C + N ------------> NaCN (if N is present)
2Na + S ----------------> Na2S (if S is present)
Na + S + C + N --------> NaSCN (if both N & S are present & insufficient amount of Na is used)
Na + X -------------------> NaX (If halogens are present)
Where
X = Cl/Br/I
Hence SFE may contain any of or all of ionic forms of respective elements.
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