[Footnote L: 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.] A slight error is introduced by the presence of a trace of oxidisable matter in the gelatin, and when very great accuracy is required, it is well to make a blank estimation of "not-tannin" without tannin infusion, and deduct 1/2 of the permanganate consumed as a correction from the not-tannin; but this may usually be disregarded. Each titration should be made twice, and successive tests should not differ by more than 0·1 _c.c._ of permanganate. Reagents.--Solutions are required of (1) Pure potash permanganate, 1 _grm._ per _litre_. (2) Pure soda or potash sulphindigotate, 5 _grm._, and concentrated sulphuric acid, 50 _grm._ per _litre_. (3) Pure oxalic acid, 6·3 _grm._ per _litre_ (decinormal). The sulphindigotate (indigo carmine), must be filtered, and when oxidised by permanganate, should give a pure clear yellow, free from any trace of brown or orange. Any contamination with indigo-purple, which gives brown oxidation-products, is quite fatal to the accuracy of the analysis. The permanganate solution is standardised by measuring 10 _c.c._ of the (decinormal) oxalic acid solution, adding a little pure sulphuric acid and distilled water, warming to 136° F. (58° C.), and running in the permanganate till a faint permanent pink is produced, for which about 32-33 _c.c._ should be required. The indigo-carmine solution should be of such strength that 14-16 _c.c._ of permanganate are required to bleach the quantity employed, which may be 20-25 _c.c._, as convenient. (4) Gelatin solution: 2 _grm._ of Nelson's or other good gelatin are allowed to swell in distilled water for two hours, melted by setting the glass in a pan of boiling water, and made up to 100 _c.c._ This will not keep. (5) Dilute sulphuric acid: 10 _c.c._ of pure concentrated acid are added to 90 _c.c._ of distilled water. (6) Good table salt. (7) Purified kaolin.