NERAL CHARCOALS.*

BY J. L. LASSAIGNE.

THE different kinds of charcoal, organic and mineral, are so varied in their uses, and their properties, established with relation to the quantity of carbon which they contain, may be so often altered by the mixture of different substances, that it is important, in a great number of cases, to be able to estimate their real value.

The object of this paper is to explain the simple processes to be used for analysing the charcoals of wood, bone, turf, and schist, so much used in domestic and industrial economy.

WOOD CHARCOAL.

This kind of charcoal, which results from the decomposition by heat of the ligneous parts of trees, contains carbon still combined with a little hydrogen, salts of potassa and lime, certain metallic oxides, and more or less moisture arising from the condensation of the vapor diffused in the air.

The proportion of water, which amounts, according to Karsten, to 9 or 10 per cent. in wood charcoal, may be accurately estimated by drying at 120° C., in a platinum crucible, a given weight of charcoal reduced to powder.

The volatile hydrogenous matters which remain united to the carbon in the different vegetable charcoals, might be appreciated, as M. Berthier did in his analysis by the dry way, by calcining, out of contact of the air, at a white-red heat, charcoal previously deprived of moisture. The difference of weight after the experiment would give the quantity of volatile hydrogenous matters. It would be preferable to burn a portion of dry charcoal by means of binoxide of copper, employing the apparatus used for the

* Journal de Chimie Médicale, February, 1843.

N. S. VOL. I.-No. IV. April, 1843.

water and the carbonic acid, which would accurately show the proportion of hydrogen and carbon.

The fixed matters composing the ordinary ash of charcoals would be obtained by the incineration, in contact with the air, of a certain quantity of charcoal. The nature and the quantity of the salts which form the ash would be known by washing it with warm distilled water, and filtering the liquor to separate the insoluble parts.

The salts soluble in water are the subcarbonate of potassa, the sulphate of potassa, the chloride of potassium, and sometimes the subsilicate of potassa. The mixture of these different salts being obtained by the evaporation to dryness of the aqueous solution, it is divided into three or four parts. One of these portions is employed for the determination of the quantity of the carbonate of potassa, by known alkalimetrical processes; the second portion is used for estimating the proportion of sulphate of potassa by means of its decomposition by a soluble salt of baryta, after having saturated the saline solution by nitric or hydrochloric acid: the weight of dry sulphate of baryta enables us to calculate that of the anhydrous sulphate of potassa to which it corresponds. The estimation of chloride of potassium is easily made with another portion of salt, whose aqueous solution, saturated with nitric acid, must be precipitated with nitrate of silver. The presence of silicic acid may be proved by supersaturating, by any acid, the alkaline solution, evaporating to dryness, and redissolving in warm distilled water.

The insoluble matters of the ash should be treated cold by weak hydrochloric acid, which decomposes and dissolves the carbonates, and renders soluble the phosphate of lime and the oxide of iron which may be found in it. The silicious sand which charcoal contains is insoluble in the latter agent.

The hydrochloric solution, supersaturated by ammonia, allows phosphate of lime and

U

peroxide of iron to precipitate, which are collected together on the same filter. Oxalate of ammonia, poured into the filtered ammoniacal liquor, precipitates oxalate of lime, which, decomposed by calcination, is converted into quicklime: finally, if carbonate of magnesia formed a constituent part of the ash, its base would be met with in the liquor from which the lime had been separated by the oxalate of ammonia; its presence would be demonstrated by phosphate of ammonia, which would precipitate it in the state of very sparingly soluble double salt.

ANALYSIS OF BONE CHARCOAL.

This charcoal, produced by the calcination of the bones of animals, is a mixture of carbon still containing hydrogen and nitrogen, phosphate of lime and carbonate of lime, with which are found associated small quantities of phosphate of magnesia, oxide of iron, alumina, silica, and some soluble alkaline salts, such as chloride of sodium, carbonate and phosphate of soda.

This charcoal, reduced to a more or less fine powder for industrial purposes, absorbs a certain quantity of humidity, which may easily be estimated by desiccation at 120o C., in an oil-bath. Thus dried, if it be calcined in the air, in a platinum or porcelain crucible, it leaves a white ash, whose weight shows, by the difference, that of the combustible matters which existed

in it.

The ash of this charcoal is entirely soluble with slight effervescence in dilute nitric or hydrochloric acid, when insoluble extraneous matters have not been added to this product, in commerce, or in its manufacture; phosphate of lime and phosphate of magnesia are isolated by its supersaturation with liquid ammonia; the precipitate collected on a filter and calcined at a red heat, afterwards gives the proportion of these earthy phosphates. The liquor from which these salts have been separated contains all the lime arising from the carbonate which existed before the solution; it may be precipitated in this state, by neutral carbonate of soda.

The quality and the quantity of the soluble alkaline salts which remain accidentally mixed with the bone charcoal, and which arise from the liquids contained in the vessels which penetrated these organs, may be estimated with facility by washing with boil ing distilled water a weighed quantity of bone charcoal, evaporating the aqueous solution to dryness to collect the various salts, and afterwards to examine them in order to ascertain their nature by the ordinary

means.

The exact proportion of pure carbon can be determined only by the combustion of a portion of very dry charcoal in a tube with binoxide of copper, operating as in the analysis of an organic substance.

The nitrogen which the charcoals of animal matters always contain, and particularly the charcoal obtained from bones, may be estimated by introducing into a combustion-tube, first a few grammes of pure and dry carbonate of lead, covering the latter with a mixture of one or two decigrammes of the charcoal to be tested, with 10 grammes of binoxide of copper, and the covering this mixture with a layer of oxide mixed with roasted copper shavings, then with a layer of copper turnings. The tube being furnished with another tube entering into a basin filled with mercury, a portion of the carbonate of lead is heated over a spirit lamp, in order to free the apparatus from air. When it is ascertained that pure carbonic acid is disengaged, a graduated bellglass, partly filled with mercury and a solu tion of caustic potassa, is placed over the orifice of the tube, and the other portions of the tube are gradually heated to redness. The gases which pass into the bellglass are carbonic acid and nitrogen; the former is easily absorbed, and the latter remains. The volume of the nitrogen is determined by taking an account of its temperature, of its pressure, and of the aqueous vapor which it may contain at the temperature at which the experiment is made.

TURF CHARCOAL.

Charcoal prepared with turf, is tender, friable, and light; it easily inflames, and burns slowly, producing a light flame without smoke. This charcoal contains carbon, composed of silica, alumina, oxide of iron, a little hydrogen and nitrogen, and ashes lime and magnesia. Its analysis may be made by the means above indicated. The residue of the incineration being treated by hydrochloric acid, and heated, leaves silica and a small quantity of alumina, which may three times its weight of hydrate of potassa. be separated by fusing this new residue with

PIT-COAL.

The varieties of pit-coal, all of which are composed of the same elementary principles,

carbon, hydrogen, oxygen, and sometimes nitrogen, combined in a multitude of different proportions, are very often mixed with argil, carbonate of iron and iron pyrites: the latter substance is injurious to the qualities of this combustible. From their properties and composition, pit-coals should be regarded as solid bitumens, whose matter is entirely mixed with the mineral substance constituting the rock in which they are

contained. The analysis of pit-coal may be made by different processes. 1st. By distilling a dry portion in order to obtain and examine the exact quantity and nature of the gases formed during this operation, and to ascertain the proportion of coke which they may yield.

The combustion, in the air, of a certain quantity of pit-coal, will show the proportion of ash, and an ulterior examination will give its composition.

The proportion of pyrites contained in pit-coal, may be determined by heating a portion reduced to powder, with a sufficient quantity of nitro-hydrochloric acid. The sulphur and the iron are converted, the former into sulphuric acid, and the latter into peroxide of iron. The solution is diluted with water, and after having beeen filtered, it is precipitated by an excess of ammonia ; the hydrated peroxide of iron is received on a weighed filter, washed, dried, and calcined at a red heat in contact with the air. By its weight, that of the pyrites may be calculated; for, according to M. Berthier, 100 of peroxide of iron are equal to 152 of pyrites.

Before the precipitation by ammonia, the quantity of sulphuric acid formed may be estimated by a solution of chloride of barium. The weight of the sulphate of baryta enables us to calculate that of the sulphur which was combined with the iron in the coal.

The proportion of protosulphuret of iron contained in cokes obtained from coals containing pyrites, may be estimated in the same manner, only in calculating, it must be borne in mind, that 100 of peroxide of iron correspond to 110 of protosulphuret of iron. In the preparation of coke, persulphuret of iron is converted by the heat into fixed and undecomposable protosulphuret.

CHARCOAL OF SCHIST.

In certain stratiform mountains, bituminous schists are met with in a very considerable layer, almost always accompanying the coaly soils. These schists, which are a mixture of argil and bitumen, furnish by calcination a light and friable charcoal. This product, which is now employed in the arts on account of its decoloring power, is sometimes substituted for bone charcoal, or mixed with it.

Charcoal of schist owes its decoloring properties to the extreme division of the carbon which it contains, and which is disseminated in a greater or smaller quantity of clay and carbonate of lime. Its analysis may easily be executed by one of the means above-mentioned. After having dried in an oil-bath a portion of pulverised charcoal, it is weighed to estimate the hygrometric

water which it contained. The residue of this desiccation is afterwards treated by boiling water in order to dissolve the sulphate of lime, whose proportion is known by the difference of the weight of the residue of this first operation. By afterwards reacting on this charcoal, thus washed with boiling water, with a weak hydrochloric acid, the carbonate of lime, which may be found naturally mixed with the schist, is dissolved without attacking either the charcoal or the argil. The proportion of the former with respect to that of the argil, may be deduced by the residue left by charcoal treated by hydrochloric acid, when it is calcined in the last place in a crucible in contact with the air. The absence of earthy phosphates in the charcoal of schist, the presence in the ashes of this charcoal of a very large proportion of silica and alumina, associated with peroxide of iron, prevent it from being confounded with animal charcoal.

ON THE NECTAR OF FLOWERS.* BY M. HENRY BRACONNOT.

THE name of nectar is given to the sweet liquor excreted in the corollæ of many plants, and with which bees prepare their honey. Naturalists suppose that the latter substance does not sensibly differ from the saccharine matter of the nectar, also regarded, by M. de Candolle, as formed of a hydrated sugar, similar to that of honey. However, it does not appear that, until now, experiment has been invoked to justify this opinion, since there exists no analysis of nectar. In the sixtythird vol. p. 102, of the Annales de Chimie, it is announced, in a note, that Fourcroy, Vauquelin and Bosc, observed on the receptacle of the flowers of the Rhododendron ponticum, grains of manna or of concrete sugar; but this saccharine matter appears not to have been analysed.

Such are the reasons which have induced me to examine nectar.

I procured this liquid from a very great number of different flowers; but as it is less disseminated in the monopetalous corollæ, I have most frequently given them the preference.

Indeed, it is necessary only to press their tube gently between the fingers, over watch glasses, or plates of glass, to obtain the nectar from them.

This liquid is saccharine, limpid, colorless, almost always uniform in most of its properties. It has no reaction on litmus paper, and is not sensibly affected by reagents, such as lime-water, baryta-water, oxalate of ammonia, nitrate of silver, and subacetate of

* Journal de Chimie Médicale, Jan. 1843.

lead; it seems to act like a solution of sugar, leaving, after evaporation and combustion, only traces of slightly alkaline ash; but this sugar is not, as is believed, similar to that of honey, for all the nectar which I have hitherto examined, has furnished, at the end of several days, in dry weather, clearly defined crystals, perfectly limpid, affecting the form of short prisms, with four or six faces, and with sharp angles; these crystals have besides all the other characters of the purest cane sugar. It constitutes, indeed, a considerable part of the saccharine matter of nectar, in which I have also detected another uncrystallisable sugar, attracting moisture from the air, and which absolute alcohol may separate, to a certain extent, from crystallisable sugar. The following is a list of flowers, in different families of the vegetable kingdom, whose nectar has constantly presented to me these two kinds of sugar :

Phlomis tuberosa.
Lavendula multifida.
Betonica grandiflora.

Lamium garganicum.
Linaria orchidiflora.
Usteria scandens.
Mimulus cardinalis.
Ruellia elegans.
Trifolium alpestre.
Fuchsia coccinea.
Polemonium coeruleum.
Bonplandia geminiflora.
Pelargonium inquinans.
Pelargonium zonale.
Lonicera caprifolium.
Houstonia coccinea.
Viola tricolor.
Lycium afrum.
Nicotiana glauca.
(Enothera suaveolens.
Gesneria coperi.
Crucianella stylosa.
Delphinium Ajacis.
Verbena teucrioïdes.
Verbena Chamædrioïdes.
Passiflora filamentosa.
Plumbago zeilanica.
Lilium croceum.
Zephiranthes grandiflora.
Fumaria lutea.
Dianthus plumarius.
Saponaria officinalis.

Citrus aurantium.

Campanula medium. Cactus Ackermanni. Cactus speciosus.

The nectars of these different kinds of flowers appeared to me, in general, to contain only slightly variable proportions of uncrystallisable sugar, and of cane sugar; however, the quantity of the latter seemed to augment sensibly in the nectar of certain flowers. Thus, that of the cactus presented,

| by crystallisation, only pure sugar, free from uncrystallisable sugar. A single flower of the cactus Ackermanni yielded nearly a decigramme. As soon as this flower has arrived at its last degree of development, and is beginning to fade, I have seen the nectar trickle from the corolla in large drops, which, falling on the ground, ultimately concreted into a very white and pulverulent crystallised sugar.

It appeared to me, in general, that the composition of the nectar of flowers may be established as follows:Cane sugar Uncrystallisable sugar Water

13

10

77

100

I have not detected in the liquid either gum, mannite, or sugar of honey.

Botanists admit that the nectar is produced by glandular bodies, situate in the vicinity of the ovary. This is true in several instances; but it must also be admitted that we are far from knowing the purpose and the structure of all these bodies of glandular appearance, and whose anomalous form is often so singular.* There are corollæ of very considerable size, which, from their structure, appear not to be in a condition to produce nectar; there are others in which the most accurate examination cannot discover any peculiar glandular apparatus, and which do not allow of the production of a very abundant saccharine excretion; so that it appears to me very probable, that the nectar often takes its origin from the rupture of the cellular tissue, deprived of the contact of light, and gorged with juices which are extravasated at the time when the corolla begins to lose its freshness. It is, indeed, in nearly analogous circumstances that the vegetable cellule forms the sugar.

Since, contrary to the received opinion, the saccharine matter of the nectar of flowers is not similar to honey, and since the concrete sugar which it yields has all the properties of cane sugar, it is evident that the latter, by remaining in one of the stomachs of the bee, undergoes an alteration, due, perhaps, to the presence of a free acid, or to any other cause, which makes it pass to the state of sugar of honey, as Hubert's experiments also prove; since it is known that that ingenious naturalist has fed bees entirely on cane sugar, at the expense of which those laborious insects continued to prepare honey and wax.