44 



Messrs. Letts and Collie on a new Method 



As regards the mechanism of the reaction, the following 

 explanation may be suggested : — 



or 

 and 



2Zn(C 2 H 5 )I + Sn = Sn(C 2 H 5 ) 2 + Znl 2 + Zn, 



Zn(C 2 H 5 ) 2 + Sn = Sn(0 2 H 5 ) 2 + Zn, 

 2Sn(C 2 H 5 ) 3 = Sn + Sn(C 2 H 5 ) 4 . 



And this explains the fact that about 50 per cent, only of the 

 tin is converted into tin tetrethyl. If the above explanation be 

 true, an alloy of zinc and tin might not be necessary; and also 

 if the conversion of the tin into tin tetrethyl takes place at 

 the moment the zinc ethiodide is decomposed by heat, the 

 action of the ethyl iodide on the couple is only to produce 

 zinc ethiodide. Several other experiments were therefore 

 made in order to ascertain as far as possible whether this is 

 the case. 



A couple was made of ordinary zinc and copper, to which 

 ethyl iodide and powdered tin were added. 



Couple used 

 =40 grm. 



Powdered 

 Tin. 



Ethyl iodide. 



Action began 

 in 



Tin tetrethyl 

 produced. 



Zn. 

 36 



Cu. 

 4 



20 grm. 



60 grm. 



15 min. 



3 grm. 



This proves beyond doubt that an alloy of the zinc and tin 

 is not absolutely necessary. 



In the next experiment, after the whole of the ethyl iodide 

 had been converted into zinc ethiodide by an alloy containing 

 15 per cent, of tin, the flask connected with an upright con- 

 denser was heated in an oil-bath for about three hours to a 

 temperature high enough to decompose the zinc ethiodide, 

 and so allow it every facility for reacting on the tin. 



Couple used = 66 grm. 



Alloy. 



Zn. 

 51 



Sn. 

 9 



Per cent. 

 Sn. 



15 



• Ethyl 

 ! iodide. 



Copper. 



grm. J 60 grm. 



Finished 

 in 



Tin 

 tetrethyl 

 produced 



20 min. 



11 grm. 



Per cent, of 



Tin con 

 verted into 

 Sn(C 2 H 5 ), 



61 per cent. 



Ethyl iodide was also allowed to act on some zinc-tin alloy 



