Royal Society. 289 



The tendency of recent theories of light has been to evade the 

 difficulty respecting the constitution of the setherial medium, by 

 seeking to discover only a representation of the facts of light by 

 analytical /onwM/te. But the grouping of facts under formulae 

 is not the same thing as comprehending them in a theory, which 

 always implies the discovery of a modus operandi. A good theory 

 of light ought to make known the characteristics of the medium 

 through which the phsenomena arc produced. 



Cambridge Observatory, 

 March 12, 1859. 



XL VII. Pi'oceedings of Learned Societies. 



ROYAL SOCIETY. 

 [Continued from p. 228.] 



June 17, 1858. — The Lord Wrottesley, President, in the Chair. 

 T^HE following communications were read : — 

 -*- "Note on Sodium-ethyle and Potassium- ethyle." By Edward 

 Frankland, Ph.D., F.R.S. 



The recent interesting discovery of sodium-etliyle and potassium- 

 ethyle by Mr. Wanklyn, led me to investigate the cause of the non- 

 formation of these bodies by reactions analogous to those success- 

 fully used for the production of zinc-ethyle and similar organo-metallic 

 compounds. In my earlier experiments upon the isolation of the 

 organic radicals, I studied the action of potassium and sodium upon 

 iodide of ethyle, and found that the latter compound was readily de- 

 composed by either of the metals at a temperature of from 1 00° to 

 130° C. The separated ethyle was, however, transformed almost com- 

 pletely into hydride of ethyle and olefiaut gas, whilst not a trace of 

 ])Otassium-ethyle or sodium-ethyle was produced. Mr. Wanklyn has 

 since repeated this experiment with the addition of ether, and has 

 obtained the same result as regards the non-formation of an organo- 

 metallic compound. 



The temperature at which sodium decomposes iodide of ethyle is 

 much lower than that at which sodium-ethyle is broken up, conse- 

 quently no explanation of the phenomenon can be obtained from 

 this source. Li his observations on the formation of ethyle*, Brodie 

 mentions that iodide of ethyle is decomposed at 1 70° C. by zinc-ethyle; 

 aud it therefore occurred to me that sodium-ethyle, owing to its more 

 powerful affinities, might effect the decomposition of iodide of ethyle 

 at a lower temperature than that at which iodide of ethyle is decom- 

 posed by sodium ; in which case the production of sodium-ethyle, by 

 the action of sodium upon iodide of etliyle, would be an impossibility. 

 Experiment completely confirmed this anticipation. A quantity of 

 a strong solution of sodium-ethyle in zinc-ethyle was thrown up into 

 a dry receiver filled with mercury, and an equal volume of pure iodide 

 of ethyle added to it. Immediately on the mixture of the two liquids, 

 * Journal of the Chemical Society, vol. iii. p. 405. 



