418 Dr. Schafhaeutl Oft the Different Species of 



that the difference between the diamond and charcoal consisted 

 only in their form of aggregation. 



Dr. S. Brown closed his highly interesting paper, read at 

 the late Birmingham Meeting, " On the Crystallization qfCar- 

 hurets" with the following remarks : " Char wood with suffi- 

 cient care, and you will obtain, not charcoal, but crystallized 

 carbon, or in other words, diamonds.^' 



When Scheele first burnt graphite or plumbago, which 

 had hitherto always been confounded with molybdena, oxide 

 of iron remained on the hearth, and graphite was declared to 

 be a carburet of iron. Berthier first showed that the iron 

 in the graphite might be extracted by means of acids without 

 any evolution of hydrogen ; Bouesnel and Karsten, burning 

 graphite in the mufile of an assay furnace, observed, that seve- 

 ral of the natural graphites, such as that from Bareros, in the 

 Brazils, left an extremely small quantity of ashes. Graphite 

 was therefore declared to be only another modification of pure 

 carbon. 



The greatest support the above theory received was from 

 the fact, first observed by Gahn, that some pieces of charcoal, 

 which had descended unconsumed through a blast furnace, 

 and fallen into the twyers, had totally changed their nature, 

 and when taken out, immediately became extinguished ; and 

 being before extremely porous, became very dense, and from 

 one of the worst conductors of caloric, they had become nearly 

 one of the best. 



In order to investigate and elucidate the before-mentioned 

 facts, I prepared carbon in as pure a state as possible, first, 

 by decomposing dry carbonic acid gas by means of po- 

 tassium; secondly, by imperfect or partial combustion of alco- 

 hol ; and thirdly, by distilling white crystallized sugar in a re- 

 tort. The three charcoals thus obtained were inclosed in as 

 many tubes of platinum, the ends of which were, after being 

 first ignited to a white heat, then hermetically welded, and 

 afterwards placed in a tube made of Stourbridge clay, filled 

 also with charcoal, and heated in a blast furnace of Sefstroem 

 till the tubes began to melt. After refrigeration, these differ- 

 ent samples of charcoal were found perfectly unaltered, both 

 in their physical and chemical properties. The same expe- 

 riment was repeated by including the same descriptions of chai*- 

 coals in a-ucibles made of Stourbridge clay ; and during a re- 

 petition of these experiments for sixteen times, in two in- 

 stances only did the charcoal alter its nature. By burning 

 these two samples in oxygen gas, as well as with alkaline car- 

 bonates, a large quantity of sUica and alumina, with traces of 

 iron, remained, and showed that the charcoal had extracted 



