Astringent Mass

Catechu forms brittle, reddish-brown masses, with a shining or opaque fracture and an astringent bitter and then sweetish taste. 

Yellowish-white to light brown, amorphous, bulky powder, flakes, or spongy masses faint characteristic odor astringent taste gradually darkens on exposure to air and light dec, 210-215°C.1... 

Gallo-tannic acid—Acidum tannicum (H. S., Br.)—is the best known of the tannins, and is obtained from nut-galls, galla (tf. S., Br.), which are excrescences produced upon oak trees by the puncture of minute insects. It appears as a yellowish, amorphous, odorless, friable mass has an astringent taste very soluble in water, less so in alcohol, almost insoluble in ether its solutions are acid in reaction, and on contact with animal tissues give up the dissolved tannin, which becomes fixed by the tissue to form a tough, insoluble, and non-putrescible material (leather). 

Characters and Tests.—Pale yellow vesicular masses or thin glistening scales, strongly astringent taste, and acid reaction. Readily soluble in water and rectifled spirit, sparingly soluble in ether. With an aqueous solution gelatin gives a yellowish-white precipitate (gelatin tannate), and ferric chloride furnishes a bluish-black precipitate (iron tannate). The acid should leave no residue when burned with free access of air. 

Characters and Tests.—Colourless, transparent,crystalline masses, exhibiting the faces of the regular octohedron, and having an astringent taste. 

Characters.—Cubes, or masses formed of coherent cubes the former about an inch in diameter, externally brown, internally ochrey-yellow or pale brick-red, breaks easily with a dull earthy fracture. Taste bitter, very astringent, and mucilaginous, succeeded by slight sweetness. Entirely soluble in boiling water. The decoction, when cool, should not be rendered blue by iodine, indicating the absence of starch. 

Characters and Tests.— White crystalline masses, slightly efSlorescent acetous odour, and sweet astringent taste. It dissolves in distilled water, and forms a clear solution, or one which has only a slight milkiness, which disappears on the addition of acetic acid. Its solution in water slightly... 

When dealing with supramolecular assemblies, the consistency of conclusions drawn by mass spectrometric analysis in the gas phase and applied to the situation in solution is always a major concern. However, sensory descriptive analyses [39-42] permit astringency to be related to our affinity scale that has been constructed on the basis of interactions between salivary proteins and selected polyphenols. 

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