ELECTEOLYTIC SYNTHESIS OF DIBASIC ACIDS. 217 



Synthetic Succinic Acid, COOH-(CH 2 ) 2 -COOH . 

 Mod =356. 



V 



fi 



100m 



K 



32 



1633 



4-59 



•0069 



64 



22-80 



641 



•0067 



128 



31-67 



8-89 



•0068 



256 



4402 



1236 



•0068 



512 



6017 



16-90 



0067 



024 



82-97 



23-31 



•0069 



k = -0068 



According to Ostwald the dissociation-constant of succinic acid is '00665.* The agree- 

 ment between the two numbers is satisfactory, and proves the identity of our synthetic 

 acid with ordinary succinic acid. 



As has been already mentioned, the yield is 60 per cent, of the theoretical amount. 



Synthesis of Adi'pic Acid. 



On first preparing ethyl potassium succinate we followed the directions of HEiNTZ,t 

 who obtained the salt by boiling succinic anhydride for several hours with absolute 

 alcohol, neutralising with potassium carbonate, and then precipitating the double salt from 

 its alcoholic solution by means of ether. The ethyl potassium succinate thus prepared 

 Heintz found to be always liquid ; in one case, however, we found it to separate as a 

 non -crystalline solid. 



We have now abandoned this mode of preparation, and avail ourselves of a generally 

 applicable method analogous to that adopted in the case of ethyl potassium malonate. 

 The diethyl ether, either by itself or diluted with a little alcohol, is introduced into a 

 roomy flask, and to it is added the calculated quantity of alcoholic potash. The whole 

 is well shaken together, and after some little time the ethyl-potassium salt falls out with 

 evolution of heat. It is not necessary, as is the case with malonic ether, to add the 

 potash drop by drop ; the whole quantity may be poured in at once. The mixture is 

 allowed to stand for some hours, and is then evaporated on the water-bath nearly to 

 dryness, a current of carbonic acid being meanwhile passed through the liquid. The 

 residue is now dissolved in water, the solution extracted with ether, and evaporated 

 down to the proper concentration. The aqueous solution thus obtained contains, besides 

 the ethyl-potassium salt, some dipotassium salt, and carbonate or bicarbonate of potassium. 

 These substances, however, are formed in the course of the electrolysis, so that their 

 presence from the first in the solution has little or no effect on the product. From the 

 ethereal extract there is re-obtained a quantity of the diethyl ether, amounting in some 

 cases to nearly one-third of what was originally taken. 



* Ostwald, Zeitschrift fiir physikal. Chem., iii. 282, 1889. 

 t Heintz, Poggendorffis Annalen, cviii. 82, 1859. 



