OF ARTS AND SCIENCES. 103 



products the more readily, the more positive the condition of the 

 molecule, so that, e. g., ethylene, CH 2 =CH 2 , is more reactive than 

 carbonic oxide, OO, because the presence of oxygen in the latter 

 substance renders the molecule more negative. For the same 

 reason, the double bond in sodic acetacetic ether, 



CH 3 - CONa 



II 

 C0 2 R - CH 



is much more reactive than in the ordinary olefine derivatives. 



Were it possible now to replace the oxygen in carbonic oxide by 

 a bivalent radical which is less negative than oxygen, as, for ex- 

 ample, by (CH 3 ) 2 , H 2 , R-N=, H-N=, the resulting compounds, 



I II III. IV. 



£j§" > C=, H 3 =0, R-X=C=, HrH>, 



would probably be more reactive than carbonic oxide, and perhaps 

 also than the olefine and acetylene derivatives : the energy of the 

 compounds must also decrease in the order, I. -IV., given. 



All attempts to isolate methylene, H 2 0, or dichlormethylene, 

 C1 2 =C=, have up to the present time been unsuccessful; especially 

 have numerous and zealous experiments been carried out in the 

 hope of isolating the hydrocarbon methylene, H 2 C= ; as, for in- 

 stance, attempts to split off water from methylalcohol, CH 3 OH, by 

 means of phosphorus pentoxide* or concentrated sulphuric acid,f 

 or to split off hydrochloric acid from methylchloride by passing 

 its vapors through red-hot porcelain tubes. $ These experiments 

 could not however be successful, since the methylene, even if 

 formed, must again unite with the reagents applied or split off. 



A most interesting experiment in this direction was carried out 

 by Butlerow,§ who found that when methjdene iodide, CH 2 T 2 , is 

 heated in a sealed tube at 100° with copper and water, there is 

 formed ethylene, CH 2 = CH 2 , and cuprous iodide. This experi- 

 ment cannot, however, be considered as proving that methylene 

 is not capable of existence, because already many unsaturated 

 compounds, especially the acetylene derivatives, show a great ten- 

 dency to potymerize, and it is therefore highly probable that such 



* Dumas, Annales de Chim. et de Phys., LVIII. 128. 

 t Regnault, Annales de Chim. et de Phys , LXXI. 427. 

 J Perrot, Ann. Chem. (Liebig), CI. 375. 

 § Ann. Chem. (Liebig), CXX. 356. 



