August 1, 1864.J THE TECHNOLOGIST. 



ON CHEMISTRY APPLIED TO THE ARTS. 19 



tion of nitrogen from the nitrates or from ammonia, as will be seen by 

 the following table : — 



Amount of Nitrogen fixed by Wheat under the Influence of 

 following Salts ; — 



Without With 



Nitrogenated Nitrogenated 

 Compounds. Compounds. 

 Phosphate of Lime and Alkaline Silicate ... 8.15 20.08 



Phosphate of Lime 7*25 19*1.7 



Earths and Alkaline Silicates..... 571 11*16 



Earth 3*U0 9.50 



Bone-black or Char. — In 1800, Lovvitz made the interesting obser- 

 vation that wood charcoal possesses the remarkable property of removing 

 colouring matters from their solutions. In 1811, Piguier also observed 

 that animal black has far greater decolorating power than wood charcoal, 

 and bone-black has consequently become one of the principal agents in, 

 sugar-refining, and has been the means, more than any other substance, 

 of producing good and cheap white sugars. To give you an idea of the 

 extent to which bone-black is used at the present day for decolorating 

 purposes in the refining of sugar, I may state that in Paris alone it is 

 estimated that about 11 million kilogrammes of bones are used 

 annually for that purpose. The preparation of bone-black is simple 

 in principle. It consists in placing in cast-iron pots about 50 

 pounds of broken boiled bones, that is, bones which have been de- 

 prived of their fat — of most of their osseine, and piling these pots ia 

 a furnace, where they are submitted to a gradually rising temperature,, 

 during twenty-four hours, such as will completely decompose the 

 organic matter, but not so high as to partly fuse the bones and thus 

 render them unfit for their applications. But a more economical process, 

 is generally adopted. It consists in introducing the crushed bones into 

 horizontal retorts, which are themselves in connection with condensers^ 

 the ends of which are brought under the retorts to assist by their com- 

 bustion in the distillation of the animal matter. By this arrangement 

 not only is char obtained, but oily matters which are used, by curriers, 

 and also ammoniaual salts employed in agriculture and manufactures. 

 The extraordinary decolorating action of animal blacks may be con- 

 sidered as partly chemical and partly mechanical — mechanical because 

 it is proved, by some interesting researches of Dr. Stenhouse, to which' 

 I shall refer further on, that the action is due to the minute division of 

 the carbon and the immense surface offered by its particles to tbe 

 colouring matter, char being composed of ninety parts of mineral salts 

 to 10 per cent, of carbon. On the other hand, the action is proved also 

 to be chemical, by the fact that water will not remove the colouring 

 matter, whilst a weak solution of alkali will dissolve it. Dr. Stenhouse's 

 valuable researches not only illustrate fully this fact, but also prove the 

 possibility of producing artificially substitutes for bone-black. In 1 857 

 he published a paper describing the production of an artificial black, 



