On the Thermoelectric Position of Carbon. 117 



points, or at least that the various units of chemical action are 

 not equivalent, and are therefore of unequal energy. Here 

 we introduce one of the higher problems of chemical meta- 

 physics. I abstain, however, from dealing with it at present. 

 If the condensation which certain hydroxides undergo on 

 heating is explicable in certain cases, there are others much 

 more numerous, which still remain without plausible expla- 

 nation, and notably is this the case with the hydroxides of the 

 elements. 



On the Oxide of Methylene, CH 2 : 0. 



There is no compound more interesting than this, from the 

 point of view of the polymerization of the metallic oxides. There 

 is a perfect parallel between the reactions by which it may be 

 obtained from its ethers and those by which certain oxides 

 are prepared from their salts. Just as the arsenious ethers 

 under the action of water give arsenious anhydride, so do the 

 methylenic ethers, when treated with water, give methylene 

 oxide, L e. its solid polymer. 



These reactions may also be compared with those which 

 give certain metallic oxides, as Sb 2 3 , Bi 2 3 , HgO, &c, by 

 the decomposition of their salts with an excess of water, or by 

 weak alkaline leys. Methylene (CH 2 ) acts in all respects 

 like a metal, and its oxide is strictly comparable to a metallic 

 oxide, with this difference, that when heated it is completely 

 depolymerized on volatilization, whereas certain oxides, as 

 (As 2 3 ) n , are only imperfectly depolymerized, whilst others, 

 such as HgO, Bi 2 3 , &c, are fixed. 



In a special paper I intend to return to the oxides and 

 chlorides of the dicarbon radicals C/ 1 , C 2 H 2 iv , C 2 H 4 ii . 



XIV. On the Thermoelectric Position of Carbon. 

 By John Buchanan *. 



[Plate VIIL] 



IN the very interesting paper read by Dr. J. A. Fleming 

 before this Society on March 14, 1885, whilst discussing 

 the question of the life of incandescent lamps, the author re- 

 marks that quite a large proportion of the carbon filaments 

 are found to break at the negative end, that is, near the point 

 where the current passes from carbon to platinum. It seemed 

 to me not improbable that the negative end of the carbon 

 might be subjected to a heating action due to the operation 



* Communicated by the Physical Society : read June 27, 1885. 



