347 



takes place. Sodium-ethyl thus stands in the same relation to iodide 

 of ethyl as hydride of zinc does to hydriodic acid ; and consequently 

 all attempts to produce hydride of zinc by the action of the metal 

 upon the hydrogen acids have failed. These considerations, taken 

 in connexion with Mr. Wanklyn's mode of forming sodium-ethyl and 

 potassium-ethyl, aiford a clue to the nature of the reactions by which 

 we shall probably eventually succeed in forming the hydrogen com- 

 pounds of the highly positive metals. Although the hydrogen com- 

 pounds of arsenic, antimony, phosphorus, and tellurium are by no 

 means exact analogues of zinc-ethyl, it would nevertheless be interest- 

 ing to ascertain the action of sodium upon these bodies, with a view 

 to the formation of hydride of sodium. 



The nature of the gas evolved by the action of sodium-ethyl upon 

 iodide of ethyl, has some interest in connexion with the formation of 

 ethyl by the action of zinc upon iodide of ethyl. Brodie expressed, 

 in the memoir above alluded to, an ingenious and highly probable 

 hypothesis, that the true source of the ethyl is the decomposition of 

 its iodide by zinc-ethyl, thus : 



and that the secondary products of the reaction (olefiant gas and hy- 

 dride of ethyl) which always accompany the ethyl, result from the 

 primary action of zinc upon iodide of ethyl, thus : 



+2ZnI. 



The composition of the gases produced in the above reaction of so- 

 dium-ethyl upon iodide of ethyl seems, however, to indicate that the 

 reverse of this hypothesis is true, and that the source of the ethyl is 

 to be found in the primary action of zinc upon iodide of ethyl, 



2(C 4 H 5 1) + 2Zn= g* g j + 2Zn I, 



whilst the secondary products are derived from the decomposition of 

 iodide of ethyl by zinc-ethyl, 



+C 4 H 4 + ZnI. 



