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When humus remains constantly damp, without, however, being covered with water, it forms a very unpleasant smelling acid, which is more particularly, characterized by the property which it possesses of colouring blue litmus paper into red. This circumstance has long been known, and it is the reason that land and meadows which are not properly drained, and which exhibit these phenomena, are called sour. We have carefully examined these facts, and have endeavoured to discover the peculiar constitution of this acid. At first, we were inclined to regard it as being of a distinct nature, and having carbon for its base; but we have since become convinced that it is generally composed of acetic acid, and occasionally contains a portion of the phosphoric. This latter always adheres so firmly to the humus that it cannot be separated from it either by boiling or washing. The liquid in which the humus is boiled certainly acquires a slight acid flavour, but the greater part of the acid remains attached to the humus. (en) |
