A Compendium of Useful Information for the Practical Man/Lime
Caustic or Burned Lime
Definition - limestone which has been burned and slaked.
Carbonated or Unburned Lime
Definition - lime in its natural state, chalk, sea shells.
Comparative Utility of Burned and Unburned Lime
Of the comparative utility of burned and unburned Lime. Is there no advantage, then, we may ask, in using caustic or burned rather than carbonated or unburned lime 1 If the ultimate effects of both upon the land be the same, why be at the expense of burning 1 Among other benefits arising from the use of burned lime, may be enumerated the following:—
1. By burning and slaking, the lime is reduced to the state of an impalpable powder, finer than could be obtained by any available method of crushing. It can in consequence be diffused more uniformly through the soil, and hence a smaller quantity will produce an equal effect. This minute state of division also promotes in a wonderful degree the chemical action of the lime. In all cases chemical action takes place between exceedingly minute particles of matter ; and among solid substances the action is more rapid the finer the powder to which they can be reduced. Thus a mass of iron or lead slowly rusts or tarnishes in the air, but if the mass of either metal be reduced to the state of an impalpable powder—which can be done by certain chemical means —it will take fire when simply exposed to the air at the ordinary temperature, and will burn till it is entirely converted into oxide of iron, or oxide of lead. By mere mechanical division, the apparent action of the oxygen of the air upon metals is augmented and hastened in this extraordinary degree ; and a similar heightening of the chemical influence of lime takes place when it is brought, in an impalpable state, into contact with the vegetable matter upon which it is intended to act.
2. The effect of burned lime is more powerful and more immediate than that of unburned lime in the form of chalk, marl, or shell sand. Hence, it sooner neutralizes the acids which exist in the soil, and sooner causes that decomposition of vegetable matter of every kind to commence, upon which its efficacy, in a great degree, depends. Hence, when it can easily be procured, it is better for our grass or arable lands, for such as contain an excess of vegetable matter, and especially for such as abound in that dead or inert form of organic matter which requires a stronger stimulus —the presence of more powerful chemical affinities, that is—to bring it into active decomposition. In such cases, tho lime has already done much good before it has been brought into tho
mild state —by exposure in the soil—and, remaining afterwards in this state in the soil, it still serves, in a great measure, the same slower after purposes, as the original addition of carbonate would have done.
3. Besides, if any portion of it, after the lapse of two or three years, still linger in the caustic state, it will continue to provoke more rapid changes among the organic substances in the soil, than mild lime alone could have done.
4. Further, quick-lime is soluble in water, and hence every shower that falls and sinks into the soil carries with it a portion of lime, so long as any of it remains in the caustic state. It thus reaches acid matters that lie beneath the surface, and alters and ameliorates even the sub-soil itself.
5. It is not a small additional recommendation of quick-lime, that limestone, by burning, loses about 44 per cent of its weight—chiefly carbonic acid—thus enabling nearly twice the quantity of lime to be conveyed from place to place at the same cost of transport. This not only causes a direct saving of money—as when the burned chalk of Antrim is carried by sea to the Ayrshire coasts —but an additional saving of labor also upon the farm—where the number of hands and horses is often barely sufficient for the necessary work.