Scientific Notices. On the employment of peat charcoal in the arts.

The London Journal of Arts, Sciences, and Manufactures, and Repertory of Patent Inventions.

Conducted by Mr. W. Newton, of the Office for Patents, Chancery Lane. (Assisted by several Scientific Gentlemen.)

VOL. XXXVI. (Conjoined Series.)

London: Published by W. Newton, at the office for patents, 66, Chancerylane, and Manchester; t. and W. Piper, Paternoster Row; Simpkin, Marshall, and Co., Stationers' Court; J. McCombe, Buchanan St., Glasgow; and Galinani's Library, Rue Vivienne,

Paris. 1850

No. CCXXI.There is, perhaps, no subject of enquiry, relating to matters of industry, which has awakened more general interest, or given rise to more sanguine expectation with regard to its influence upon the condition of a certain class of the community, at least, in Ireland, than the application of peat, on an extended scale, as fuel for domestic purposes, and in some branches of manufacture.

The prominent manner in which this question has been treated by individuals, whose position is sufficiently elevated to give them credit in the eyes of the world, has probably led, in many respects, to a false conception of its true merits; at the same time, the extensive introduction of peat into use as a substitute for other descriptions of fuel, promises advantages too great to be treated of slightingly.

Peat, as is pretty generally known, is a substance of vegetable origin; a substance apparently still in a state of transition, still undergoing those chemical changes which sufficed, in the early ages of the world, to convert whole forests into the vast carbonaceous deposits encountered in certain localities, under the form of coal. The conversion of vegetable matter into peat, is a process which, under favorable circumstances, such as the presence of moisture and the accumulation of the vegetable substance in large masses, seems to be constantly in progress; and immense tracts of peat are doubt lessly, at the present time, in process of formation. Peat is met with principally in damp marshy districts, on the borders of rivers, the course of which is impeded, so that their waters become partially stagnant; and particularly in the neighbour hood of the embouchure of great rivers, which flow through a low country. It is also encountered, in some cases, at a great height above the level of the sea,—peat bogs existing in the elevated vallies of the Alps, and also in the mountain ous regions in the north-western part of South America.

In its natural state the use of peat, as fuel, is limited, both from its want of calorific power, and from its containing a large proportion of volatile matter, the odour of which is penetrating, and easily imparted to matters in its neighbourhood. When peat is, however, previously burned to charcoal, or, more properly speaking, to a kind of coke, it is converted into a fuel of most valuable character, nearly approaching, if not quite equal to, wood charcoal, and the coke from coal, and possessing some qualities superior to either of them.

In a country where, as in England, an apparently unlimited supply of excellent fuel can always be obtained without difficulty, both for the purposes of manufacture and for domestic use, we are apt to lose sight, or to become regardless, of the advantages that may be found in the conversion of a substance like peat to a useful object; but it ought to be borne in mind, that the coal measures are probably not exhaustless; indeed, it has been publicly stated, by an unquestionable authority on such a subject, that the day when England will see the end of her coal is not so far distant as we are disposed to believe; it is therefore, even in this respect, an object of interest to see the enormous tracts of peat which cover many square miles of country, rendered available to the ends of industry, even if it were only with reference to the economising the great source of our national supremacy. With respect to the employment of peat-charcoal, there are some circumstances to be considered which serve to give it a fair title to superiority over both wood-charcoal and coke: in its application to metallurgic processes, for example, particularly in the manufacture of iron, its superiority is well marked; and in many manufacturing processes, where a continued moderate heat is requisite, this kind of fuel is very much better than either coke or wood-charcoal. The value of peat-coke, as fuel, arises from its peculiar composition; and partly from its physical character. Owing to its being somewhat friable and cavern ous, it ignites readily, and, when once lighted, burns entirely away, even when in small fragments. The amount of heat it produces in burning is somewhat less than that of wood-charcoal, weight for weight; and it bears almost the same relation to coke; but it is more lasting than charcoal, and, from its chemical constitution, more suitable to metallurgic purposes than coke. Most varieties of coal contain sulphur in the form of iron pyrites, and some, sulphate of lime also, which, as well as the pyrites, is a source of sulphur, as it becomes converted into sulphuret of calcium in the process of coking. Now, in almost all metallurgic opera tions, the presence of sulphur is highly deleterious, as it is apt to form a combination with the metal under treatment, and so produce an injurious effect. This defect; when coke is used, attains a high pitch, unless the coke be prepared with great care and skill, so that the sulphur may be partially expelled or burned off during the process of burning: in coke prepared in retorts, or in gas-making, the presence of the sulphur is an effective bar to its employment in the arts. The objection arising from the noxious influence of sulphur cannot certainly be urged against wood-charcoal; but this substance possesses, when compared with the coke from peat, a physical disadvantage: — from its light porous structure it burns away with great rapidity; and (although, from its purity, well suited to almost every operation in the arts) on this account it becomes too costly to be employed, excepting under circumstances in which no substitute for it can be made by coke or other fuel. At all times charcoal must be a very costly fuel, both in consequence of the limited supply of the raw material, and from the expense of manufacture. Peat-coke offers a substitute for charcoal under all circumstances, and under almost all for common coke as well. Peat seldom contains sulphur in any state; and even when that substance is present, it is in such small quantity that it is generally oxidized and expelled in the process of coking the peat.

After having been dried, peat yields, when burned, about twothirds of its weight of coke equal to wood-charcoal; and it has been calculated that this may be produced and sold for about 35s.per ton; at which price it would compete, in the market, with coke from coal, and possess a great advantage in price over charcoal;—in this case, we suppose the peat-coke to be prepared according to the present method of burning charcoal, or of making coke from coal in ovens. Peat contains, how ever, a certain proportion of matters having commercial value, which, being volatile, are driven off during its combustion, and, consequently, lost; these are, acetic acid, ammonia, and certain volatile oils, partaking of the nature of naphtha. See ing that these valuable matters are lost in the process of carbonizing the peat in ovens, it has been proposed to carry on the process of conversion in retorts of brick or iron, to approximate the process to the manufacture of gas from coal, or that of the extraction of acetic acid and other products from wood. This idea does not, however, with respect to peat, appear to possess much practical value; it is a question whether the quantity of the products above named be sufficient to cover the increased expense of working;—for, in the first place, the amount of peat-coke produced at each opera tion is reduced, inasmuch as the retorts must be limited in size; and, secondly, a great additional expense is incurred for fuel to heat the retorts, which, being closed from the air, require to be heated entirely from the outside; and, as a given quantity of peat requires the consumption of a quantity at least equal to its own bulk, to burn it into eharcoal, it is clear that one-half of the charcoal from the whole will be lost; and is to be compensated for by the volatile products collected from that peat contained within the retort;—the process being also in every way more laborious, and, consequently, more expensive. In the process of coking the peat in ovens, the peat burns itself,—the volatile matters are certainly all lost; but every ton of peat yields its proportion of coke, which is its most valuable commercial constituent.

In the manufacture of iron, it is a question whether peat-charcoal may not be entirely substituted for every other kind of fuel with striking advantage to the manufacturer, with respect both to the quantity and quality of the iron produced. It was suggested long ago by Berthier that peat might be used with advantage in the extraction of iron from its ores; and he also hinted at the advantage that might be gained by mixing the pounded ore with the charcoal, compressing the whole into the size and form of bricks, and thus placing them in the furnace;—the iron ore and carbonaceous matter would thus be brought into a degree of proximity that would probably much facilitate the reduction and fusion of the metal—at the same time that a fuel was employed incapable of producing upon the iron any injurious effect.

The employment of a fuel derived immediately from the sterile bogs which cover so many thousands of acres of land otherwise available to agriculture, would be in itself an in ducement to promote the introduction of peat-charcoal into more general use; but happily the benefit would be here as much to the arts adopting the innovation as to the agents of its immediate production.

T. W. K.