The infusion, for which 20 _grm._ of hemlock bark or a corresponding quantity of other material must be used, is made by exhausting with 2 or 3 quantities of water successively, first cold, and then with heat (by placing the flask in a pan of boiling water), each portion of water being poured off into a _litre_ flask. The last should be almost colourless. The liquor is thus made up to nearly 1 _litre_, 25 _c.c._ of dilute sulphuric acid (about 1 vol. concentrated in 10) is added, and the liquor is filtered through a small filter, which is finally rinsed with a small quantity of water. Liquid ammonia is now added till the liquor slightly smells of it, and, if any precipitate is formed, it is filtered off as before; 25 _c.c._ of dilute sulphuric acid is again added (which should give the liquid an acid reaction), and it is made up to 1 _litre_. The titration is done as described under Löwenthal's method, but instead of precipitating with gelatin, 100 _c.c._ is mixed with 100 _c.c._ of a solution of copper sulphate to which sufficient ammonia has been added to redissolve the precipitate first formed, and containing 1-1/4 per cent. of copper sulphate. This is well shaken and filtered, and the "not-tannin" is determined in the filtrate just as with gelatin; a little dilute sulphuric acid being added in the basin to neutralise the ammonia. The writer has examined this method with regard to a few tanning materials. With valonia (and therefore probably with oak bark) the preliminary treatment is unnecessary, and copper precipitation gives results practically identical with the improved gelatin, while it is less troublesome. On the other hand, a sample of Miller's Hungarian Larch Extract which gave tannin equal to 18·08 per cent. (by the gelatin method) gave no precipitate with cuprammonic sulphate, and hence a result in tannin of _nil_ by Darton's method. It is worth remark that by the copper method it is therefore possible to estimate the valonia tannin alone in a mixture of larch and valonia tannin. Probably this mode of analysis may also be utilised to separate other tannins. With chestnut extract the results seem satisfactory, as regards the precipitation of the tannin by copper, the figures agreeing very closely with those by gelatin, but the preliminary treatment with sulphuric acid and ammonia precipitates about 75 per cent. of what is usually reckoned as tannin, leaving 7·53 per cent. of tannin only instead of 25·53 per cent. as reckoned by the gelatin method; which, judging by practical results in tanning, can hardly be accepted as correct. The results of the gelatin method are found to agree fairly with those of direct absorption by hide-powder, which is strong confirmation that what is estimated as tannin is what is absorbed by the hide. It is well known that sulphuric acid precipitates many tannins, and in an experiment with cutch it was found by the writer that saturation with salt and the addition of dilute sulphuric acid as