Tan
or TANNERS' WASTE. This consists of the bark of various trees, chiefly the Oak, Larch, and Willow. The tannin is extracted for the purpose of tanning leather, and a large quantity of refuse remains to be disposed of. This refuse is frequently employed for making hotbeds, as it gives a steady heat for a considerable time, the heat being more easily regulated, and retained longer, than that obtained from pure stable-yard manure. In general, however, a mixture of manure and dead leaves is preferred to Tan, as, when it has lost its heat, and has to be replaced in the hotbed, this mixture forms a valuable manure for the soil; while Tanners' Waste decays slowly, and is of little value as manure. Analysis shows that the nitrogenous matters of the fresh bark are almost entirely removed from it in the processes of extracting the tannin; while some of the tannin remains, and hinders decay of the refuse. Nearly half the weight of the Tan is water; and the ash, or mineral compounds in the Tan, consists very largely of Carbonate of Lime, and of Silica; the valuable Phosphates and Potash salts being present in it only in very small quantity. If employed as manure, Tan should be made up into a compost with earth, lime, and farmyard manure, and the whole should be saturated occasionally with liquid manure, and allowed to ferment for a considerable time before it is used.