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W. M. Green reported that in prolonging the steeping of tea from 10 to 20 minutes, he observed the formation of a tannate of theine, which diminished the proportion of 1.30 per cent. of theine at 10 minutes to 1.16 per cent. after 20 minutes steeping, a loss of about 10 percent., unless the latter salt so formed is proved to yield up its theine constituent in the human stomach.
No two give identical reactions at all events not when mixed with the iron tannate to form the pigment in writing. "It is owing to the difference in these provisional colouring matters that it is possible to distinguish between writing written with different kinds of ink. I was able easily to obtain samples of the inks used by the Vandams, by Mrs. Popper, by Mr. Farrington, and by the druggist.
We should first soak the piece of cotton in a solution of tannic acid, and then pass it into a solution, say, of tartar emetic, when the tannic acid will be firmly fixed, as tannate of antimony, on the cotton. We then dip the mordanted piece of cotton into the colour bath, containing, for instance, Magenta, and it is dyed a fine red, composed of a tannate of antimony and Magenta.
"That gives us about half an hour or three-quarters here if a conveyance is obtainable, that is." "A gelatine lozenge dropped into the tea cup precipitates the tannin in the form of tannate of gelatine," said the clergyman to Miss Mergle, in a confidential bray. Jessie stood up, and saw through the window a depressed head and shoulders over the top of the back of a garden seat.
In the case of tartar emetic, it is the tannate of antimony which remains upon the cloth, a compound of considerable stability, and almost perfectly insoluble in water; in the case of a few colors fixed by the arsenical alumina mordant, the arsenic is in an insoluble state of combination with the alumina, in fact, the poisons are in the presence of their antidotes, and not even the most scrupulous manufacturer has any fear that he is turning out goods which can be hurtful to the wearer.
But tannic acid, alone, does not form very fast lakes with Magenta and the other basic dyestuffs, and so a means of rendering these lakes more insoluble is needed. Perchloride of tin, in a similar manner, yields insoluble tannate of tin with tannic acid.
Delage at Roscorf used a liquid containing salts of magnesia and tannate of ammonia to produce the same result. In his latest book on the Origin of Life Dr. Charlton Bastian tells of using two solutions. One consisted of two or three drops of dilute sodium silicate with eight drops of liquor fern pernitratis to one ounce of distilled water.
The original pigment say blue or blue-black ink is placed in the ink, to make the writing visible at first, and gradually fades, giving place to the black of the tannate which is formed. The dyestuffs employed in the commercial inks of to-day vary in colour from pale greenish blue to indigo and deep violet.
Delage at Roscorf used a liquid containing salts of magnesia and tannate of ammonia to produce the same result. In his latest book on the Origin of Life Dr. Charlton Bastian tells of using two solutions. One consisted of two or three drops of dilute sodium silicate with eight drops of liquor ferri pernitratis to one ounce of distilled water.
A Chinese being interviewed for the Cook says: Drink your tea plain. Don't add milk or sugar. Tea-brokers and tea-tasters never do; epicures never do; the Chinese never do. Milk contains fibrin, albumen or some other stuff, and the tea a delicate amount of tannin. Mixing the two makes the liquid turbid. This turbidity, if I remember the cyclopædia aright, is tannate of fibrin, or leather.
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