Bone char

Bone char (Latin: carbo animalis) is a porous, black, granular material produced by charring animal bones. Its composition varies depending on how it is made; however, it consists mainly of tricalcium phosphate (or hydroxylapatite) 57–80%, calcium carbonate 6–10% and carbon 7–10%. It is primarily used for filtration and decolorisation. Bone char (Latin: carbo animalis) is a porous, black, granular material produced by charring animal bones. Its composition varies depending on how it is made; however, it consists mainly of tricalcium phosphate (or hydroxylapatite) 57–80%, calcium carbonate 6–10% and carbon 7–10%. It is primarily used for filtration and decolorisation. Bone char is primarily made from cattle and pork bones; however, to prevent the spread of Creutzfeldt–Jakob disease, the skull and spine are no longer used. The bones are heated in a sealed vessel at up to 700 °C (1,292 °F); the oxygen concentration must be kept low while doing this, as it affects the quality of the product, particularly its adsorption capacity. Most of the organic material in the bones is driven off by heat, and was historically collected as Dippel's oil; that which is not driven off remains as activated carbon in the final product. Heating bones in an oxygen-rich atmosphere gives bone ash, which is chemically quite different.