ELECTROLYTIC SYNTHESIS OF DIBASIC ACIDS. 213 



of this Society* the expectation that salts of the type E'DOC'E^COOK (where E' is a 

 univalent and E" a bivalent alcohol radical), which are thus at once potassium salts 

 and esters, would behave electrolytically as salts of monobasic acids. An experiment of 

 Guthrie's shows that the ester group plays no active part in electrolysis. Guthrie found 

 that on the electrolysis of the salt KOS0 2 *OC 2 H 5 , his anode of amalgamated zinc was 

 attacked with formation of the corresponding zinc salt, Zn(OS0 2 'OC 2 H 5 ) 2 ,t which proves 

 that the anion was composed of the unchanged group , S0 2 'OC 2 H 5 . One would there- 

 fore expect the anion of the salt C 2 H 5 OOC-E"-COOK to be C 2 H 5 OOC-E"COO, which, 

 if platinum electrodes were used, should decompose according to equations I. to III. 

 Equation I. would then read as follows : — 



2C 2 H 5 OOCR"COO = C 2 H 5 OOC-R"-E"-COOC 2 H 5 +2C0 2 ; 



that is, from the ethyl-potassium salt we should obtain the diethyl ether of a higher acid 

 of the same homologous series. This expectation we were able to realise, for from 

 ethyl potassium malonate we obtained by electrolysis diethyl succinate. In a similar 

 way we have prepared adipic acid from succinic acid, sebacic acid from adipic acid, 

 suberic acid from glutaric acid, and from suberic and sebacic acids two new acids of the 

 oxalic series. 



It is evident from the mode of formation that the acids thus prepared must be 

 symmetrical (provided we leave stereo-chemical relations out of account) ; and, in especial, 

 from normal acids we obtain normal acids, as the following examples illustrate : — 



2C„H 5 OOC-CH 2 -COO = C 2 H 5 OOCCH 2 -CH 2 -COOC 2 H 5 +2C0 2 

 2C 2 H 5 OOCCH 2 CH 2 COO = C 2 H 5 OOCCH 2 CH 9 CH 2 CH 2 COOC 2 H 5 +2C0 2 

 2C 2 H 5 OOC(CH 2 ) 4 -COO = C 2 H 5 OOC(CH 2 ) 8 COOC 2 H 5 + 2C0 2 



The method then gives us the means of ascending the oxalic series of acids synthetically, 

 and that by the greater steps the further we advance in the series. As yet we have not 

 pushed the process beyond the normal acid containing a chain of eighteen carbon atoms, 

 but we hope shortly to take the next step, and prepare the acid with a chain of thirty-four 

 carbon atoms. 



With regard to the practical working of the method, we have found that in order to 

 obtain a successful result there are certain conditions which must be observed, and these 

 perhaps may be best illustrated in the special case of the synthesis of succinic ether. 



The vessel in which the electrolysis took place was a platinum crucible, 4" 8 cm. high 



and 4 - 3 cm. in diameter. This served at the same time as the cathode. The anode was 



made of a stout platinum wire bent in corkscrew fashion, and distant all round about 



1 cm. from the wall of the crucible. The relatively small area of the anode occasioned a 



great current density at its surface, — a condition extremely favourable for the electrolysis 



proceeding according to equations I. to III. It is a priori clear that the greater the current 



density at the anode is chosen, the closer will the discharged anions be packed, and there- 



* Crum Brown, Proc. Roy. Soc. Edin., 1889-90, p. 53. 

 t Guthrie, Ghem. Soc. Quar. Jour., ix. 131, 1856. 



