Effects of Animal Charcoal on Solutions. 121 



M. Ix>witz first discovered this property of charcoal in 1791. 

 He used only charcoal of wood. M. Guilbert observed, that 

 the discolouring power of wood charcoal was improved by ex- 

 posing it for a considerable time, in a wet state, to the rays of 

 the sun. In 1810, M. Figuier, professor of chemistry at Mont- 

 pellier, discovered that animal charcoal discoloured with much 

 greater power. It has subsequently been used very extensively 

 by the sugar- refiners of France in clarifying their syrups. Of 

 bone or ivory-black, one-sixth of the weight of the raw sugar 

 is boiled with it for ten minutes. The charcoal and impurities 

 are separated by filtering, and the syrup is filtered a second 

 time to separate a little charcoal which comes through the first 

 filter, (Payen ) In the Journal de \Pharmacie, torn, iv., 

 pp. 301 — 7, there is a distinct account of the mode of pre- 

 paring bone-black, by M. Cadet de Gassicourt ; and in the 

 same work, tom. viii., pp. 257 — 277, an excellent memoir on 

 charcoal, considered as a discolouring substance, by A. Bussy, 

 which was crowned by the Society of Pharmacy of Paris, and 

 contains everything known on the subject. It is followed by 

 another memoir on the same subject by M. Payen, to which a 

 second prize was adjudged. The substance of the preceding 

 memoir is given in this Journal, vol. xiii., pp. 403 — 16. 



But the action of animal charcoal on solutions has been 

 considered hitherto only in reference to the removal of colour- 

 ing matters. More determinate results, however, might be ex- 

 pected in solutions of saline and other chemical bodies, of 

 which the composition is known. The investigation is also 

 interesting, from the light which it may throw upon the state 

 of combination in which bodies exist in cases of ordinary solu- 

 tion, as salt in water, to which (he doctrine of definite propor- 

 tions seems wholly inapplicable. If a solid body, such as 

 carbon, destroy such a combination, and take down the saline 

 matter attached to its surface, we may conclude that there is 

 an analogy between the combination of the salt with the water, 

 and the combination of the salt with the charcoal, and that 

 the former as well as the latter processes have something of a 

 mechanical character. 



The same property is possessed by other solid bodies, in a 

 state of minute division, as when newly precipitated, although 

 not in so great a degree. And, in analytic researches, its 



