Note L — Chapter VI

Hunt (Jour. Soc. Chem. Industry, April 1885) states, that saturation with salt causes partial precipitation of gallic acid when present, and that results agreeing more closely with those obtained by absorption with hide are obtained by employing a mixture of 50 c.c. liquor, 25 c.c. 2 per cent. gelatin solution, and 25 c.c. saturated solution of salt containing 50 c.c. of concentrated sulphuric acid per litre and a teaspoonful of kaolin. This approaches very nearly to Löwenthal's original method, but with the addition of the kaolin, and as in it, it is to be feared that a portion of the tannate of gelatin will remain in solution. For accurate work, therefore, absorption by hide-raspings is preferable, though even that has been shown by the writer to remove gallic acid and other matters beside tannin. Hunt states that raw hide also absorbs catechin.