868 Prof. H. E, Armstrong on Lotv- Temperature Research 



Properties and Structure of Carbox. 



The differences, which are both quahtative and quantitative, 

 between various kinds of charcoal depend probably both on differences 

 in porosity and on differences in composition. Charcoal is by no 

 means a single substance but contains more or less hydrogen, oxygen 

 and nitrogen ; the amount of actual carbon, in an uncombined form, 

 which is present in it cannot even be surmised. 



xinalyses of blood charcoal, for example, show that it may contain 

 nearly 2 per cent, of hydrogen, 7 of nitrogen and 15 of oxygen, 

 together with about 6 per cent, of mineral matter. Soot will contain 

 over 60 per cent, of carbon, together with 7 or 8 of oxygen. Sugar 

 charcoal may contain nearly 20 per cent, of oxygen. 



Whatever the composition of charcoal may be, even if it consist 

 entirely of compounds which are all but carbon, its properties are very 

 nearly those of carbon in the amorphous state. It is therefore desir- 

 able to consider the peculiarities of amorphous carbon in elucidation 

 of the remarkable power which charcoal possesses of attracting gases. 

 In view of the very different behaviour of the three forms of carbon, 

 it is almost certain that in the amorphous state it offers structural 

 peculiarities which condition its special activity as an absorbent : 

 there are two points of view, from which these peculiarities may be 

 considered with advantage — the one being that of the genetic relation- 

 ship of charcoal to carbon compounds, especially the hydrocarbons, 

 the other that of its colour. 



Genesis of Amorphous Carhon. — Of all the elements, carbon is the 

 most remarkable on account of the endless multiplicity of compounds 

 to which it gives rise, over 130,000 being already known. The 

 properties of the element are to be inferred from the study of this 

 vast host. By considering the peculiarities, by contrasting and corre- 

 lating the idiosyncrasies of the various compounds, the chemist is 

 eventually enabled to paint a picture of the ideal substance symbolised 

 by the letter C — the symbol significant of the carbon unit or atom ; 

 that is to say, of the elementary material carbon but not of any of 

 the forms of carbon actually known to us, the presumption being that 

 these are all substances of great molecular complexity the formation 

 of which is a consequence of peculiarities inherent in the carbon atom. 



The potentialities of tiie carbon atom are best elucidated by refer- 

 ence to the behaviour of the hydrocarbons — the compounds formed 

 by the association of hydrogen with carbon. The simplest of these, 

 which is represented by the formula CH4, methane or marsh gas, is a 

 saturated compound; nothing can be combined with it but one or 

 more of the hydrogen atoms it contains may be displaced by another 

 radicle of equivalent value in combining power — chlorine or bromine 

 or iodine, for example. Taking the hydrogen atom as the unit, the 

 atom fixing power or valency of carbon is indicated by the fact that 



