230 On the Action of Sodium and Ethyl-iodide on Ace tic Ether. [Feb. 24, 



Exp. 2. " 5 cub. centims. of good acetate of ethyl and 0'3 gvm. of sodium 

 were sealed up in a small glass tube and heated in a water-bath to 100° C. 

 until all the sodium had disappeared. The tube was then opened under 

 water ; the evolved gas measured 25 cub. centims. at ordinary temperature, 

 but at 0° C. and 760 millims. pressure and dry it measured 23 cub. centims. 

 If the volume of hydrogen be calculated, which is equivalent to 0*3 grm, 

 sodium, it will be found to be 140 cub. centims." 



Exp. 3. "Another specimen of acetic ether, which was prepared with 

 greater care, evolved no gas by the action of potassium or sodium." 



It is thus evident that whilst we allowed all evolved gas freely to escape, 

 Mr. Wanklyn operated in sealed tubes under great pressure, — an alteration 

 in the conditions of the experiment which might well lead to a modification 

 of the result. Mons. L. Cailletet has recently shown that the evolution of 

 hydrogen from zinc and hydrochloric acid is gradually diminished and 

 finally stopped under increasing pressure ; and the same chemist also finds 

 that the evolution of hydrogen from sodium-amalgam and water is dimi- 

 nished and finally stopped in a sealed tube. It follows from these experi- 

 ments that pressure retards or even interrupts a reaction in which a per- 

 manent gas is evolved, whilst it is known to exercise little or no influence 

 upon other chemical changes in which no evolution of gas takes place. 

 This influence of pressure upon certain kinds of chemical action affords an 

 explanation of the difference between the results of Mr. "Wanklyn's experi- 

 ments and our own, as regards the evolution of hydrogen during the action 

 of sodium upon acetic ether. "We can confirm his observation that sodium 

 dissolves in valeric ether, under ordinary atmospheric pressure, without the 

 evolution of any gas. A reaction, whatever its nature may be, which thus 

 proceeds readily with ethylic valerate can scarcely be impossible with its 

 homologue, acetic ether, and it is probable that this reaction goes on side 

 by side with those which we have described in our memoir ; but when the 

 pressure is moderate those changes chiefly take place which involve the 

 disengagement of hydrogen, whilst under the great pressure arising in 

 sealed tubes these changes are more or less suppressed, and the reaction 

 observed by Mr. Wanklyn comes into prominence. 



Lastly, Mr. Wanklyn's own experiments scarcely justify his unqualified 

 opinion that "equations which assume evolution of hydrogen in these 

 reactions are inadmissible." In two out of three of his experiments, hy- 

 drogen in considerable quantity was evolved ; and although in experiment 

 No. 2, given above, he attributes the hydrogen to the presence of alcohol, 

 yet in experiment No. 1 its origin cannot be so explained, as he states 

 expressly that the acetic ether employed "had been very carefully deprived 

 of alcohol and water ;" yet the proportion of hydrogen evolved in this case 

 was much larger than in experiment No. 2. 



We reserve our observations upon Mr. Wanklyn's views regarding the 

 changes which take place when sodium acts upon acetic, butyric, and 

 valeric ethers, until the publication of the experimental data upon which 

 those views are founded. 



