Bone Black, a black carbonaceous powder, obtained by grinding the product of bones burned in a close vessel at a red heat. The name ivory black should properly be limited to the finer and more expensive article prepared from ivory. The volatile products of the distillation of bones are an empyreumatic oil, fetid gases, and ammoniacal vapors. The latter may be collected, as they sometimes are, in forming with them salts of ammonia. The fixed products, which constitute animal charcoal, or bone black, consist of:

Carbon......

...9.6

Sulphate of lime........

.. 0.2

Carbonate of lime......

.. 8.6

Phosphate of lime..........

...78.3

Phosphate of magnesia......

.. 1.3

Chloride of sodium.......

.. 0.5

Silicate and sand..............

......0.8

Protoxide of iron....

....0.2

Alkalies ,and sulphur........

....0.5

100.0

The powder resembles that of vegetable charcoal, but is more dense and less combustible, and its ashes are not so readily soluble in sulphuric acid as those of charcoal. The process of preparing the material varies according as the ammoniacal vapors are saved, or allowed to go to waste. In the former case the bones, cleaned of their fatty matters, are carbonized in cast-iron cylinders, which connect by a three-inch pipe with the condensing apparatus. The cylinders are kept at a red heat for 36 hours, when the charred bones are taken out, and the cylinders are refilled. The bones are then ground in mills. The volatile products are in some instances discharged under the fire, by which they are consumed, and their disagreeable odor destroyed. In this way also they afford some heat, and save fuel. By the other process, the bones are put in cast-iron pots, which contain each about 25 lbs., and these are put together in pairs, mouth to mouth, and luted. They are then piled up in an oven or kiln, the entrances to which are tightly bricked up, except those for the admission of the flame from the furnace connected with the kiln, and the opening into the chimney.

The pots are well heated for 16 to 18 hours by the flame playing around them, and this is increased by the combustible vapors which issue from the bones. Other arrangements have been contrived for consuming the disagreeable gases. - The valuable property possessed by bone black is its absorbing completely the color of organic solutions, and leaving the liquid clear and limpid; this is greatly facilitated by heating the mixture to the boiling point. Vegetable charcoal possesses the same property also, but to a much less degree. From the year 1800 wood coal continued to be used for decolorizing crude sirups, for which purpose it was about this time recommended by Lowitz, a chemist of St. Petersburg; but in 1811 M. Figuier of Montpellier discovered the greater efficiency of animal charcoal for this purpose, and this being employed the next year by Derosne and Payen, it has since superseded the use of vegetable coal. Although this property of charcoal has been ably investigated by distinguished chemists, as Bussy, Payen, and Derosne, it does not yet clearly appear upon what it is dependent, nor whether it acts mechanically or chemically.

M. Bussy has shown that bone black used for decoloring an indigo solution in concentrated sulphuric acid, and this diluted with water, does not give the slightest trace of sulphate of indigo by repeated washings, but does of free sulphuric acid. Treated, however, with an alkaline wash, the charcoal gives up the indigo, thus appearing as if it acted mechanically. The efficiency of the charcoal is greatly dependent upon its being in a minute state of division. The earthy matters combined with the carbon of bones, no doubt, have great influence in effecting this condition. Vegetable coal attains it to some extent, and the decolorizing property also, by being finely comminuted previous to charring, and mixed with pulverized pumice, quartz, or calcined bones, or with some chemically acting ingredient, as carbonate of potassa. The most powerful decolorizer is charcoal obtained in the manufacture of Prussian blue by calcining animal matter with potassa. It is the purest form of charcoal, freed by the potassa from its nitrogen, and reduced by chemical segregation to the finest particles.

Carbon obtained by decomposing carbonate of soda also possesses this property in a high degree, from the fine state of division in which its particles are found, so that it would appear to be by no means peculiar to animal charcoal. Even other substances than carbon are observed to possess the same property, as has been shown by E. Filhol, such as sulphur, arsenic, iron reduced by hydrogen, etc. Bone black that has been once used for refining sirups may be revived, so as to answer the same purpose again. The process consists in thoroughly washing out the saccharine matters absorbed, and in some establishments in dissolving the lime, which is also taken up by the bone black, by fermentation in water acidulated with hydrochloric acid. The charcoal is then again calcined in crucibles, or, as in France, in reverberatory furnaces. High steam is said also to restore its property, but this cannot remove the lime. Several forms of furnace have been contrived in England to effect this purpose; and retorts are used which hold 50 lbs. of charcoal, and in which the re-burning is completed in 15 or 20 minutes. - Besides extracting the color of fluids, animal charcoal takes away the bitter principle from bitter infusions, and iodine also from its solutions; and it is found by Graham that various inorganic substances are abstracted from their solutions, as lime from lime water, and metallic oxides, as lead, from solution in water.

Bone black is also used to extract from spirits distilled from grain the volatile poisonous oil, called fusel oil, which gives to the liquors a disagreeable taste. It is also a disinfecting agent. - For chemical and pharmaceutical purposes, bone black requires to be purified, that is, freed from the phosphate and carbonate of lime which constitute its principal part. Dilute hydrochloric acid is used to dissolve these out, and the residue, being well washed, is pure animal carbon. It is used to absorb the active principles of plants from their boiling infusions. The charcoal, after being well washed and dried, is mixed with boiling alcohol, to which it imparts the principle it has absorbed from the vegetable infusion, and an alcoholic extract is obtained. The alcohol then may be distilled off, and the pure substance recovered. Quinia, strychnia, and many other vegetable principles, are thus procured. - The refuse animal black of the sugar refiner is largely used as a manure, and in the manufacture of phosphorus and of baking powders. From the investigations of M. A. de Romanet, it appears that, in old soils exhausted of humus, it produces no effect, having none of this substance to restore to the soil.

But it gives out the ammonia it had taken up in the sirups, and neutralizes the bitter and acid principles of healthy or new soils; the phosphates it contains are also rendered soluble in water, and are thus furnished to grains requiring them.