108 GIBBS. 



normal carbonate has been converted into the acid carbonate according to 

 the equation : " 



CrH, . on . COOCH.,+Na„CO.,=CV,H, . Oil . C00jSTa+CH30H+ 



NaHCO., 



To i^rove that this is the end point of the reaction, or at least the point 



where the ra'te is exceedingly slow, the ester was shaken for da3's with jniTe 



N 



— sodium acid carbonate " solution in a number of sealed tubes. Wliile 



10 



a slight reaction was noted, it is lielieved that the sul:)stances were 

 practically in equilibrium.^" Any reaction taking place is not suf- 

 ficiently rapid to afEect the accuracy of the analytic methods previously 

 described, which depend upon sodium acid carbonate for the removal of 

 salicylic acid as sodium salicylate from the presence of the methyl ester, 

 without saponification of the latter. 



Cahours -" says that concentrated solutions of alkalies react with 

 methyl salicylate in the cold to produce the salts of the ester. Freer -^ 

 has prepared sodium salicylic ethyl ester by the action of sodium upon 

 the ester and by the action of sodium hydroxide upon the ester in 

 etherial solution. He mentions the fact that the compound thus formed 

 is easily hydrolized by moisture. The reactions with dilute solutions of 

 sodium hydroxide and sodium carbonate, here described, are hydrolytic."- 

 Analyses of the solutions at the end points of the reactions, prove tliat 

 the products of the saponifications are present in the amounts indicated by 

 the theory. 



" The hydrolytic dissociation of sodium hydrogen carbonate according to the 

 equation: NaHC03-f-H,0 ?= NaOH+HX03 necessitates a gaseous pressure of 

 carbon dioxide and a continuous loss of the gas with formation of normal sodium 

 carbonate in the solvition. A discussion of this question may be more fully 

 entered into a later paper. It is sufficient here to note tliat the effect due to 

 this cause is very slight. 



'^ The amoimt of the hydroxide in this solution is very small. McCoy, Am. 

 Chem. J. (1903), 29, 4.53, has calculated the concentration to be 2.9X10"^. 



"A more detailed discussion will be taken up in a later paper. 



=°Ami. CImn. Phys. (1844) (3) 10, 327. 



^Am. Chem. J. (1892), 14, 411. 



''- Secondary reactions take place, to a small extent, not sufficient to affect 

 the accuracy of the method. Some of these, probably due to light rays, are 

 being studied. 



