July 20, 2024

Agar: Physical and chemical tests / Analysis of crude drugs

Agar: Physical and chemical tests / Analysis of crude drugs


To identify the chemical characteristics of a given sample.

1.Boil 1gm of agar with 10ml of  water until the solution is affected, cool to room temperatureA slip jet is formed. (Jelly-like mass is formed)Agar
2.0.2% solution of agar, + aqueous solution of tannic acidNo Precipitate is formedDistinction  from gelatin3.Warm little sample in an alcoholic solution of Pot. HydroxideCanary     yellow     colour      is producedAgar present
4.Mount a small quantity of powder in the solution of ruthenium red and examine microscopicallyParticles  acquire  red  or  pink colourPresence of mucilage in agar.
5.Add 1 drop of N/10 solution of iodine to 10ml of decoction of agar. Rapidly cool under tap water to room temperature.Crimson or Pale yellow colour is producedAgar is present
6.Add 0.5ml of conc. HCl to 4ml of 0.5% solution of agar. Heat it in a water bath for 30minutes, cool at room temperature and divide it into two portions. Add 3ml of 10% NaOH solution and Fehling’s solution A and B in equal quantities and warm over a water bath. Add 10% of barium chloride solution. Red  ppt  of  cuprous  oxide  is obtained Slight   white   ppt  of  barium sulphate                                  is obtained          Reducing  sugars are present
7.Incinerate agar to ash, and add a drop of con.HCl observe under the microscopeFragments of diatomsAgar is present


The above morphological characteristics and chemical tests indicate that the crude drug is Agar.


Kokate CK. Practical Pharmacognosy, 4 edition, VallabhPrakashan. Delhi; 1994: 98.

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ER20-11T Pharmaceutics TheoryER20-21T Pharmacology Theory
ER20-11P Pharmaceutics PracticalER20-21P Pharmacology Practical
ER20-12T Pharmaceutical Chemistry TheoryER20-22T Community Pharmacy & Management Theory
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ER20-13T Pharmacognosy TheoryER20-23T Biochemistry & Clinical Pathology Theory
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BP301T Pharmaceutical Organic Chemistry II TheoryBP401T Pharmaceutical Organic Chemistry III Theory
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