CARBON, 355 



SEC. II. CARBON carbo Latin. 



1. ITS IMPORTANCE AND WIDE DIFFUSION. 



(a.) An element of great interest, diffused through the animal and 

 vegetable kingdoms, and largely in the mineral, either in the form of 

 carbon or carbonic acid, free or combined. 



(b.) Known to the ancients. Theophrastus Eresius, pupil and suc- 

 cessor of Aristotle, mentions charcoal 300 hundred years before 

 Christ, and Pliny describes the process of burning it.* 



2. PRINCIPAL NATURAL FORMS AND VARIETIES. 



(a.) DIAMOND. It differs from charcoal, in being a non-conduc- 

 tor of electricity, and in nearly all its physical properties ; still it 

 is pure crystallized carbon. 



The proof rests on the fact, that it is entirely combustible ; that it 

 is converted into carbonic acid gas, without any other product ; and 

 that it forms steel by cementation with soft iron.f The combustion 

 is effected without difficulty, in pure oxygen gas ; under the compound 

 blowpipe, and in melted nitre. It differs from charcoal more in 

 its state of aggregation,! than in its chemical relations. Still it is 

 much harder than we imagine ; a mass of vegetable charcoal is light, 

 because a great quantity of matter has been expelled in the aeri- 

 form state, and thus the substance is made to appear both soft and 

 light ; but its integrant particles^ are hard, as will be peceived by 

 grinding them between plates of window glass which they will 

 scratch, and it is stated on the authority of Prof. Leslie, that 

 the sp. gr. of charcoal is really greater than that of the diamond. 

 Carbon exists in a transparent state, in the oils and in alcohol, and in 

 crystals of white sugar, from all of which it is easily developed, by 

 heat, acids, and other agents ; it is found also in several gases. 



(b.) PLUMBAGO, or black lead. The proof that this is nearly pure 

 carbon, is the same ; it produces carbonic acid by combustion, and 

 there is only a small residuum of iron and earthy impurities. || 



(c.) ANTHRACITE. The same remark may be made of this ; it 

 is nearly pure carbon. 



There seems no reason to doubt that the globules which I obtained 

 in 1823, from the plumbago and anthracite, by the deflagrator, arose 

 in part, from the earths present in these minerals ; but with charcoal, 

 I conceive it to have been otherwise, (see note, p. 358,) and the 



* Parkes' Essays, Vol. I, 396. t Phil. Trans. 1815, p. 371. 



| Charcoal is not more different from diamond, than clay or pure pulverulent alu- 

 mina is from the sapphire ; or chalk from Iceland crystal ; or pulverulent magnesia, 

 from the same in the boracite ; or than quartz nectique, (swimming flint,) from rock 

 crystal. 



So, the integrant particles of pumice stone and tripoli are hard, although the 

 mass is soft, and that of the former is very light. 



|| For its analysis, see Am. Jour. Vol. X, p. 102. 



