The Analytical Review, 112-113 (Jan. 1792)

ART. XV. Memoire sur l'Analyse chymique de la Tourbe, &c. On the chemical Analysis of Turf, and the Mode of converting it into Charcoal; by Mr. de Bullion; Journal des Sçavans.

Turf, says Mr. B., is composed of the remains of various plants of marshes. In it we find the shells of water snails, and of other little animals of the worm kind, a little earth, and quartsoze sand. I have distilled half a pound of turf, in a glass retort, in a sand-bath capable of making the retort redhot, and obtained from it two ounces of water, mixed with a little volatile alkali, and about four drams of thick congealed empyreumatic oil, which melts at 25° of Reaumur. A large quantity of inflammable air was disengaged, possessing the same properties as what I have distilled from wood. The coal left in the retort had no smell, and weighed half as much as the turf. This charcoal burns very well, gives a very strong fire, and affords a pretty considerable quantity of ashes, which I lixiviated. The lixivium afforded me, on evaporation, selenite, regenerated calcareous earth, shell-lime, a little marine salt with an earthy base, and a little liver of sulphur, afforded by the decomposition of the selenite. From this we may judge, that the charcoal of turf contains nothing injurious to the health, that it may be employed for the same purposes as charred wood, and that it is preferable to pit-coal, which contains pyrites, and consequently sulphur with other mineral substances that may be insalubrious. Turf cut in square pieces and dried serves as fuel. Mr. de Carolle has found a method of converting these into very fine and good charcoal. I have compared it with that of wood, in furnaces exactly similar in the open air. That of wood lasted one hour; that of turf, two; and the latter appeared to me to give a stronger heat. By means of it I have vitrified fused sand of copper-ore from which I had extracted the metal. I also forged and welded, at a smith's forge, with this charred turf, two bars of iron, an inch square, in less than ten minutes.

To convert turf into charcoal, Mr. de C. has invented a furnace constructed in the following manner. He makes, with bricks, a round tower, fifteen feet in diameter, and three and half high, the walls of which are fifteen or sixteen inches thick. Six inches from the ground an iron grate is fitted in, supported here and there by bricks. Its bars are an inch distant from each other. The turf well dried is thrown into this furnace, without any regular arrangement, till it is as high as the wall: it is then carried up eight or nine feet higher, in the shape of a cone, and this cone is covered with straw slightly wetted, which is afterwards plastered over with earth. The turf is then set fire to at four openings, of six or seven inches wide, made close to the ground. Four other openings are to be left, in the intervals between these, two feet from the ground, to admit air at discretion, that the fire may burn equally throughout. When the cone sinks and cracks, sand and wet earth are to be thrown on, as is done by those who char wood. When the cone is sunk to the level of the walls, it is to be covered with five or fix inches of earth or sand, and all the openings are to be stopped up. In this state it is to be left four days The holes at the bottom are then to be opened, to admit air into the heap, which contains a great deal of pyrophorus, that requires twelve hours longer to consume. After this the holes are to be again stopped, and in four days the charcoal is to be taken out. Sometimes pieces will again take fire on being exposed to the air, when wet earth or sand must be thrown on them, for which purpose there should always be some at hand. This charcoal may be employed instead of charred wood, in all cases, and is preferable to pit-coal for burning in fireplaces in the English fashion. Thirty sacks of turf will afford about twenty of charcoal.

Turf may also be employed as manure: but for this purpose it must have previously been put underneath animals, mixing it with their litter; and it is to be observed, that, without this, no good manure can be made from any vegetable substance.