THE ELEMENTS AND JJFE 391 



extract the carbon from the gas, and there is no other means 

 known hj which this can be done at ordinary temperatures. 

 The chemist has to use the electric spark, or very high tem- 

 peratures, to perform what is done by the green leaves at the 

 ordinary temperatures in which we live. 



The reverse operation of combining carbon with other ele- 

 ments is equally difficult. In Chambers's Encyclopaedia we 

 find the following statement: '^ At ordinary temperatures all 

 the varieties of carbon are extremely unalterable ; so much so 

 that it is customary to burn the ends of piles of wood whirh 

 are to be driven into the ground, so that the coating of non- 

 decaying carbon may preserve the inner wood. Wood-charcoal, 

 however, burns very easily, animal charcoal less so ; then fol- 

 low in order of difficulty of combustion coke, anthracite, black- 

 lead, and the diamond." The two latter withstand all tem- 

 peratures, except the very highest obtainable. These various 

 states of carbon differ in other respects. Ordinary carbon is 

 a good conductor of electricity; the diamond is a non-con- 

 ductor. 



Carbon unites chemically with almost all the other elements, 

 either directly or by the interv^ention of some of the gases. It 

 also possesses, as Sir Henry Roscoe says : " A fundaiTiental and 

 distinctive quality. This consists in the power which this ele- 

 ment possesses, in a much higher degree than any of the others, 

 of uniting with itself to form complicated compounds, contain- 

 ing an aggregation of carbon-atoms united with either oxygen, 

 hydrogen, nitrogen, or several of these, bound together to form 

 a distinct chemical Avhole.'' 



Carbon is also the one element that is never absent from 

 any part or product of the vegetable or animal kingdoms ; and 

 its more special property is that, when combined with hydro- 

 gen, nitrogen, and oxygen, together with a small quantity 

 (about 1 per cent) of sulphur, it forms the whole group <if 

 substances called albuminoids (of which white of egg is the 

 type), and which, much diluted, forms the essential part of 

 the blood, from which all the solids and fluids of organisms 



