THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



♦ 



[THIRD SERIES.] 



APRIL 184y. 



XXXIII. On the Existence and Effects of Allotro^nsm in the 

 constituent elements of Living Beings. By John William 

 Draper, M.D.y Professor of Chemisti-y in the University of 

 New York"^. 



IT has been completely established for the majority of ele- 

 mentary substances, that there are several forms under 

 which each may occur ; forms which differ entirely both in 

 their physical and chemical relations. 



Thus, in the case of carbon, many such forms are known. 

 To three of them M. Berzelius has directed attention: — 1st, 

 ordinary charcoal; 2nd, plumbago; 3rd, diamond. They 

 are three distinct modifications of the same element. They 

 dilfer in specific gravity, in specific heat, and in conducting 

 power, both for electricity and caloric. In their relations 

 to light, the first perfectly absorbs it and is black ; the 

 second reflects it like a metal; the third is transparent like 

 glass. When crystallized, plumbago and diamond do not 

 belong to the same system : their chemical relations are also 

 strikingly different. Charcoal takes fire with facility, and 

 some varieties of it are even spontaneously combustible in the 

 air ; but crucibles and furnaces are made of plumbago because 

 of its incombustibility ; and the diamond with difficulty is set 

 on fire in pure oxygen gas. 



It seems immaterial to what class elementary bodies belong, 

 whether electro-negative or positive : they present analogous 

 results. Silicon, sulphur, selenium, phosphorus, titanium, 

 chromium, uranium, tin, iridium, osmium, copper, nickel, 

 cobalt, iron, oxygen, chlorine, are cases in point ; and the 

 instances which appear as exceptions are rapidly diminishing 

 in number. 



* Communicated by the Author. 

 Phil. Mag. S. 3. Vol. 34. No. 229. April 1 849. R 



