Tannic acid salts

The fastness of basic dyes can be improved by after-treatment with tannic acid, in order to convert the dyestuff into its comparatively insoluble tannic acid salt. The wet-fastness is further improved by the action of an antimony salt which forms an even more insoluble dye-tannic acid-antimony complex. The most convenient antimony compound to use is tartar emetic , w hich is a popular name for potassium antimony tartrate, 2(K(Sb0).C4H40g).H20. The treatment is carried out in the following manner the dyed goods are worked in a bath containing 1 per cent of... 

The pomegranate alkaloids, pelletierine (46) and pseudopelletierine (48) as well as minor accompanying bases, have a long history as salts of tannic acid as an anthelmintic mixture for intestinal pinworms (see Antiparasitic AGENTS, ANTHELMINTICS). The alkaloids themselves (as the taimates) are obtained from pomegranate tree (Punkagranatum L.) root bark and are among the few bases named after an individual (P. J. Pelletier) rather than a plant. 

Preparation of Alkaloid III Tannate 20 g of Alkaloid III was dissolved in 200 ml of isopropyl alcohol at room temperature and a mixture of 30 g of tannic acid dissolved in 300 ml of isopropyl alcohol, maintained at 40 to 50 C was added thereto with rapid stirring. The mixture was cooled to 20 C, filtered and the precipitate dried at about 80 C. There was thus obtained 33.5 g of the tannate salt of Alkaloid III, as a pale yellow amorphous powder, relatively insoluble in water, and having an indefinite melting point. 

Astringents such as tannic acid (home remedy black tea) or metal salts precipitate surface proteins and are thought to help seal the mucosal epithelium. Protein denaturation must not include cellular proteins, for this would mean cell death. Although astringents induce constipation (cf AP salts, p. 166), a therapeutic effect in diarrhea is doubtful. 

The ferric salts of benzoic, succinic, hydroferrocyanic, gallic and tannic acids are sparingly soluble in cold water, while basic ferric salts of formic and acetic acids formed on boiling are also sparingly soluble. Solutions of ferric thiocyanate and salicylate exhibit characteristic colorations. 

In 1853, it was demonstrated that coca leaves contained tannic acid and a peculiar bitter principle, resin, tannin, an aromatic principle, extractive, chlorophyll, a substance analogous to theine, and salts of lime. In 1855, the crystalline alkaloid erythroxyline was discovered in coca leaves, which was called cocaine. The earlier methods for isolating cocaine were as follows ... 

Mordant is a compound that is combined with dye to make it fast or less likely to lade. Some mordants contain metallic salts that can change or enhance the dye color. Compounds commonly used as mordants include alum, Glauber s salts, tannic acid, tin (stannous chloride), and copperas (iron sulfate). 

B. A sample solution, when added to a solution of an alkaloidal salt, albumin, or gelatin, produces a precipitate. Assay Not less than 96% of Tannic Acid, calculated on the dried basis. 

Mix 2 drops 5 per cent tannic acid (tannin) solution with 2 drops 20 per cent silver nitrate solution, and place the mixture upon drop-reaction paper or upon a little cotton wool. Hold the paper in the vapour produced by heating an ammonium salt with sodium hydroxide solution. A black stain is formed on the paper or upon the cotton wool. The test is a sensitive one. 

Cupric salts in 0-00001 N-concentration can be detected by the formation of a turbidity with a mixture in solution of an alkali-metal thiocyanate and either gallic acid, tannic acid, catechol, or quinol.5... 

Slot and Geuze (1) improved the sodium citrate method for reducing gold salt by the addition of tannic acid to the reaction. The reaction rate, and hence the aze of the gold, could be controlled by the amount of tannic acid added, and monodisperse gold sols, ranging in size from 3 to 17 nm could be produced. 

Precipitated Protein Salts.—Other acids, e.g. picric, phospho-timgstic and tannic acids, precipitate albumins from solution in the form of insoluble protein salts. The alkali salts of these acids cause no precipitation. These precipitation tests are used in salting out methods for the separation of the proteins, but the limits of differentiation are not sharp and much care is needed to make the separations valuable. More specific details as to methods of manipulation may be found in laboratory texts on physiological chemistry. 

Inks.—Formerly all writing inks except so-called India ink, which is a carbon product, were made by the treatment of ferric salts with tannin or tannic acid. The green solution produced with excess of the iron salt becomes black on drying and exposure to the air. Such iron inks may be bleached by means of oxalic acid which reduces the colored ferric compound, produced with the gallotannic acid, to a colorless compound. At the present time many writing inks are made from aniline dyes. These are not bleached with oxalic acid, but are... 

Alkaloids are invariably found in combination with acids forming salts which dissolve in water or alcohol. They are composed of carbon, hydrogen and nitrogen. Some contain oxygen. They are precipitated from saline solutions by the addition of alkalies. They are mostly colorless and crystallizable. They can be precipitated by one or more of the following alkaloidal reagents tannic acid, gold chloride, phospho-molybdic acid, picric acid and potassio-mercuric iodide. 

Gelatin will also react with aldehydes and aldehydic sugars, anionic and cationic polymers, electrolytes, metal ions, plasticizers, preservatives, and surfactants. It is precipitated by alcohols, chloroform, ether, mercury salts, and tannic acid. Gels can be liquefied by bacteria unless preserved. 

Most basic and acid dyestuffs are fixed without aid by animal fibres vegetable fibres, on the other hand, require the intervention of a special mordant. Tannic acid is generally used along with basic dyestuffs, as it forms insoluble salts with these compounds. 

Cotton possesses the power of attracting a certain amount of tannic acid from solutions containing this body, and of retaining it even after washing. Cotton prepared in this manner may be dyed with most basic dyestuffs just as well as wool. In practice the cotton treated with tannic acid is further submitted to the action of tartar emetic or some other antimony compound. An insoluble salt of tannic acid and antimony oxide is formed, and... 

The base is, yellowish brown, and is obtained by precipitating the violet solution of one of the salts with an alkali. It forms a bluish-green solution with concentrated sulphuric acid, and on dilution the colour changes through blue to violet, a violet precipitate being formed finally. It dyes a dull blue shade on cotton mordanted with tannic acid. 

The saffranines are dyed on cotton mordanted with tannic acid, and produce the shade of their monoacid salts. Unmordanted cotton is capable of fixing small amounts of saffranine. 

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