To identify the chemical characters of a given sample.
Test and Observations
|Boil 1gm of agar with 10ml of water|
until the solution is affected, cool to room
|A slip jet is formed. (Jelly like|
mass is formed)
|0.2% solution of agar, + aqueous solution|
of tannic acid
|No Precipitate is formed||Distinction from|
|Warm little sample in alcoholic solution|
of pot. Hydroxide
|Canary yellow colour is|
|Mount a small quantity of powder in the|
solution of ruthenium red and examine
|Particles acquire red or pink|
the mucilage in agar.
|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|
|Agar is present|
|Add 0.5ml of conc. HCl to 4ml of 0.5%|
solution of agar. Heat it on the water bath for
30minutes, cool at room temperature and
divide into two portions.
a) Add 3ml of 10% NaOH solution
and Fehling’s solution A and B in equal
quantities and warm over the water bath.
b) Add 10% of barium chloride
|Red ppt of cuprous oxide is|
Slight white ppt of barium
|Incinerate agar to ash, add a drop of|
con.HCl observe under the microscope
|Fragments of diatoms||Sulphate in agar|
From the above morphological characters and chemical tests, the given crude drug is identified as Agar.
1.Kokate CK. Practical Pharmacognosy, 4 edition, VallabhPrakashan. Delhi; 1994: 98.
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