142 A VISIT TO A BONE BOILING FACTORY. 



of which the same elements, by arranging themselves differently, pro- 

 duce two or more different substances. 



This is the case in the present instance. On exposing bone shavings 

 even to a lamp heat, they are observed immediately to become black ; 

 shewing that the new compounds that are the result of this decom- 

 position are not capable of combining with the whole of the carbon, but 

 that part remains in the state of charcoal intimately mixed with the 

 earthy matter. This mixture goes by the name of bone-black, or animal 

 charcoal. 



Part of the carbon combines with part of the oxygen, and forms 

 carbonic acid, while part of the hydrogen and part of the nitrogen pro- 

 duce ammonia ; the carbonic acid and the ammonia, as they are formed, 

 combine and prod uce carbonate of ammouia, which, therefore, is another 

 of the useful substances resulting from the decomposition of bone. Part 

 of the oxygen and hydrogen combine and produce water ; and part of 

 the oxygen, the hydrogen, and carbon, by combining, produce a volatile 

 oil of a strong and peculiar odour, which goes by the name of animal 

 oil. The remainder of the carbon and hydrogen, with probably some 

 nitrogen, combine and produce an inflammable gas. Thus the decom- 

 position in close vessels of the single substance, bone, produces five new 

 substances ; namely, animal charcoal, carbonate of ammonia, animal 

 oil, water, and an inflammable gas. A low red heat volatilises all these 

 substances, except the first ; which, therefore, when the process is per- 

 formed on a large scale in iron vessels, remains in the retort separated 

 from the other four compounds. The water, the carbonate of ammonia, 

 and part of the oil, are condensed, and remain in the receiver ; the in- 

 flammable gas, holding in solution another part of the oil from which it 

 derives an inconceivably nauseous odour, passes off through a pipe, and 

 is either conveyed into the ash-pit of the furnace, whence it is drawn up 

 among the burning fuel and is consumed, or is set fire "to as it issues 

 from the mouth of the pipe ; by either of which methods its noisome 

 smell is for the most part avoided. The ammoniacal liquor likewise 

 combines with a little of the oil, from which, however, it may for the 

 most part be separated by redistillation ; enough, however, of the oil 

 remains united with it to produce that particular modification of odour 

 by which spirit of hartshorn (for so this substance is commonly called) 

 is distinguished from pure ammonia ; or, by other processes, unneces- 

 sary here to mention, the ammonia is obtained entirely free from the 

 oil. 



As animal charcoal is the great product in Messrs. Cowan's esta- 

 blishment, our guide kindly explained to us the process of producing it 

 which is thus : the bones are put into cast-iron retorts, which are care- 

 fully sealed — the furnace being heated to a great temperature for about 

 6 to 12 hours, according to the nature of the bones. As will naturally 

 be presumed a waste occurs, 3j cwt. of bones will produce from 2 to 



