Peat and its Uses as Fertilizer and Fuel. Samuel W. Johnson
change. They have been procured, however, by the action of muriatic acid on sugar. They are indifferent in their chemical characters, are insoluble in water and in solution of carbonate of soda; but upon heating with solution of hydrate of soda they give dark-colored liquids, being in fact converted by this treatment into ulmic and humic acids, respectively, with which they are identical in composition.
The terms ulmic and humic acids do not refer each to a single compound, but rather to a group of bodies of closely similar appearance and properties, which, however, do differ slightly in their characteristics, and differ also in composition by containing more or less of oxygen and hydrogen in equal equivalents.
After complete extraction with hydrate of soda, there remains more or less undecomposed vegetable matter, together with sand and soil, were these contained in the peat.
Crenic and apocrenic acids.—From the usually yellowish liquid out of which the ulmic and humic acids have been separated, may further be procured by appropriate chemical means, not needful to be detailed here, two other bodies which bear the names respectively of Crenic Acid and Apocrenic Acid. These acids were discovered by Berzelius, the great Swedish chemist, in the water and sediment of the Porla spring, in Sweden.
By the action upon peat of carbonate of ammonia, which is generated to some extent in the decay of vegetable matters and is also absorbed from the air, ulmic and humic acids are made soluble, and combine with the ammonia as well as with lime, oxide of iron, etc. In some cases the ulmates and humates thus produced may be extracted from the peat by water, and consequently occur dissolved in the water of the swamp from which the peat is taken, giving it a yellow or brown color.
Ulmates and Humates.—Of considerable interest to us here, are the properties of the compounds of these acids, that may be formed in peat when it is used as an ingredient of composts. The ulmates and humates of the alkalies, viz.: potash, soda, and ammonia, dissolve readily in water. They are formed when the alkalies or their carbonates act on ulmin and humin, or upon ulmates or humates of lime, iron, etc. Their dilute solutions are yellow, or brown.
The ulmates and humates of lime, magnesia, oxide of iron, oxide of manganese and alumina, are insoluble, or nearly so in water.
In ordinary soils, the earths and oxides just named, predominate over the alkalies, and although they may contain considerable ulmic and humic acids, water is able to extract but very minute quantities of the latter, on account of the insolubility of the compounds they have formed.
On the other hand, peat, highly manured garden soil, leaf-mold, rotted manure and composts, yield yellow or brown extracts with water, from the fact that alkalies are here present to form soluble compounds.
An important fact established by Mulder is, that when solutions of alkali-carbonates are put in contact with the insoluble ulmates and humates, the latter are decomposed; soluble alkali-ulmates and humates being formed, and in these, a portion of the otherwise insoluble ulmates and humates dissolve, so that thus, in a compost, lime, magnesia, oxide of iron, and even alumina may exist in soluble combinations, by the agency of these acids.
Crenates and Apocrenates.—The ulmic and humic acids when separated from their compounds, are nearly insoluble, and, so far as we know, comparatively inert bodies; by further change, (uniting with oxygen) they pass into or yield the crenic and apocrenic acids which, according to Mulder, have an acid taste, being freely soluble in water, and in all respects, decided acids. The compounds of both these acids with the alkalies are soluble. The crenates of lime, magnesia, and protoxide of iron are soluble, crenates of peroxide of iron and of oxide of manganese are but very slightly soluble; crenate of alumina is insoluble. The apocrenates of iron and manganese are slightly soluble; those of lime, magnesia, and alumina are insoluble. All the insoluble crenates and apocrenates, are soluble in solutions of the corresponding salts of the alkalies.
Application of these facts will be given in subsequent paragraphs. It may be here remarked, that the crenate of protoxide of iron is not unfrequently formed in considerable quantity in peat-bogs, and dissolving in the water of springs gives them a chalybeate character. Copious springs of this kind occur at the edge of a peat-bed at Woodstock, Conn., which are in no small repute for their medicinal qualities, having a tonic effect from the iron they contain. Such waters, on exposure to the air, shortly absorb oxygen, and the substance is thereby converted into crenate and afterwards into apocrenate of peroxide of iron, which, being but slightly soluble, or insoluble, separates as a yellow or brown ochreous deposit along the course of the water. By further exposure to air the organic acid is oxidized to carbonic acid, and hydrated oxide of iron remains. Bog-iron ore appears often to have originated in this way.
Gein and Geic acid.—Mulder formerly believed another substance to exist in peat which he called Gein, and from this by the action of alkalies he supposed geic acid to be formed. In his later writings, however, he expresses doubt as to the existence of such a substance, and we may omit further notice of it, especially since, if it really do occur, its properties are not distinct from those of humic acid.
We should not neglect to remark, however, that the word gein has been employed by some writers in the sense in which we use humus, viz.: to denote the brown or black products of the decomposition of vegetable matters.
It is scarcely to be doubted that other organic compounds exist in peat. As yet, however, we have no knowledge of any other ingredients, while it appears certain that those we have described are its chief constituents, and give it its peculiar properties. With regard to them it must nevertheless be admitted, that our chemical knowledge is not entirely satisfactory, and new investigations are urgently demanded to supply the deficiencies of the researches so ably made by Mulder, more than twenty years ago.
Elementary Composition of Peat.
After this brief notice of those organic compounds that have been recognized in or produced from peat, we may give attention to the elementary composition of peat itself.
Like that of the vegetation from which it originates, the organic part of peat consists of Carbon, Hydrogen, Oxygen and Nitrogen. In the subjoined table are given the proportions of these elements as found in the combustible part of sphagnum, of several kinds of wood, and in that of a number of peats in various stages of ripeness. They are arranged in the order of their content of carbon.
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