312 . Royal Society, 



gen 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 hy- 

 drogen from sodium-amalgam and water is diminished and finally 

 stopped in a sealed tube. It follows from these experiments that 

 pressure retards or even interrupts a reaction in which a permanent 

 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 experiments 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 un- 

 qualified opinion that "equations which assume evolution of hy- 

 drogen in these reactions are inadmissible." In two out of three of 

 his experiments, hydrogen in considerable quantity was evolved ; and 

 although in experiment No. 2, given above, he attributes the hydro- 

 gen 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. 



